This feature is exclusive to Bedrock Edition.

This is the scripting documentation for Bedrock Edition beta 1.13.0.5. New features, components, and capabilities in this release are not final and might change without notice before the final release (1.13.0). Be sure to check the documentation once the release is out of beta if the add-on isn't working properly. Resource and behavior packs created for the beta are not guaranteed to work on the final release.

Scripting System [ edit ]

The Minecraft Script Engine uses the JavaScript language.

You can write JavaScript scripts and bundle them with Behavior Packs to listen and respond to game events, get and modify data in components that entities have, and affect different parts of the game.

Demos [ edit ]

Here are some demos to help you get started with scripting. Unzip them to check out the code, or import them as a .mcpack to play with them

Demo Last Updated Download Link Turn-Based RPG April 17, 2019 [1] Mob Arena April 17, 2019 [2]

Known Issues [ edit ]

This is the list of currently known issues with the Minecraft Script Engine

Issue Workaround Scripts are not loaded properly from archived packs Unzip script packs before applying them to a world. If you import a script pack with the .mcpack extension, it will unzip it for you Custom UI doesn't work in VR or MR mode Currently you will only be able to use custom UI when running the game in regular mode Custom UI doesn't retain state upon suspend and resume Currently there's no workaround for this issue Exiting a world without scripts and entering one that has scripts might cause the wrong world to load Restart Minecraft before loading a new world with scripts Calling removeEntity on a dying entity might cause the game to crash Don't call removeEntity the same frame you reduced the entity's damage to 0. Removing the entity forces it to be removed right away. Instead, save any dying entities and clean the up on the next frame (See the Turn-Based Demo for an example of this)

Breaking Changes [ edit ]

While we continue to work and refine the experimental Scripting API we might need to make changes that will break your current scripts. Please check this section if your scripts aren't working as expected.

Category Change UI engine.on now takes a facet name. In order to check for the script engine starting and connect it to the UI you will need the following: engine.on("facet:updated:core.scripting", ...); Followed by the following line after you are done doing your initialization: engine.trigger("facet:request", ["core.scripting"]); Components Calls to getComponent now return the component's parameters inside of the 'data' parameter of the return object. Events Event data objects now hold the event's parameters inside of the 'data' parameter of the event data object. Events Custom events need to be registered before using. Check the documentation for registerEventData for more information. Events Custom events need to have a namespace and can't use the 'minecraft' namespace. This namespace is reserved for built-in events only. Events Event Data is now standardized. Call createEventData to create an event data object prefilled with all the fields and default values for an event. You will need this event data object to trigger any events.

In this section you will find the list of minimum and recommended software you will need to make your own scripts.

NOTE: Scripts are only supported on Windows 10 PCs at the moment. If you try to open a world with scripts on a device that doesn't support scripts, you will see an error message letting you know you can't enter the world.

Software Minimum Recommended Code Editor Visual Studio Code or any plain-text editor Visual Studio Community 2017 with the following components installed: 'JavaScript diagnostics', 'JavaScript and TypeScript language support', 'Just-In-Time debugger' Debugger N/A Visual Studio Community 2017 Other Vanilla Behavior Pack available from [3] Storage 1.0 GB of free space for text editor, game, and scripts 3.0 GB of free space for Visual Studio, game, and scripts

Getting Started [ edit ]

First you will need to download the latest Vanilla Behavior Pack. You can get this from the following link: https://aka.ms/behaviorpacktemplate

Once you have downloaded the Behavior Pack, unzip it to a folder. Inside the Behavior Pack you will find the scripts folder which contains all the scripting files you want to run.

In the scripts folder you will find two folders: one for client scripts and one for server scripts.

Server Scripts: These scripts run on the server side of the game. This includes spawning new entities, adding components, or modifying components on an entity.

Client Scripts: These scripts run on each individual player's side of the game. This is a good place to respond to events and manage anything specific to the player.

Once you have chosen whether you are making a client or server script, simply add a new blank text file with .js extension to the appropriate folder, and open it in your preferred code editor. Then code away! You can have as many or as few JavaScript files as you want here (the name of the files doesn't matter) and they will all be run independently of each other!

Once you have finished making changes and wish to test the script in game, compress the file to .zip format then change the extension from ".zip" to ".mcpack". Double click on the .mcpack file to import it into Minecraft. Make a world and activate the pack in your world to test it. https://www.minecraft.net/en-us/addons/

NOTE: For scripts to be run by the game, you need to enable Experimental Gameplay on the world where you will run scripts on. This will be necessary while scripting is still in beta.

When entering a world that has client scripts in it, you will be prompted to accept that you wish to run scripts on your device (this will show up both for local worlds as well as multiplayer worlds).

Additionally, if your pack contains client scripts, you need to include a client_data module in the pack's manifest. This tells the game anything in the scripts/client folder needs to be sent over to the clients. Please refer to the Add-on Documentation page for more information on the pack's manifest contents.

Folder Structure

Example of manifest module needed for client scripts

{ "description" : "Example client scripts module" , "type" : "client_data" , "uuid" : "c05a992e-482a-455f-898c-58bbb4975e47" , "version" : [ 0 , 0 , 1 ] }

vanilla_behavior_pack

root folder /scripts /client > myClientScript.js /server > myServerScript.js > manifest.json > pack_icon.png

Structure of a Script [ edit ]

In this section you can find a quick description of the basic structure of a JavaScript script file for the Minecraft Script Engine. If you would like to learn more about JavaScript or want to follow a fundamentals tutorial, you can check the official documentation on the Mozilla Developer Network here: https://developer.mozilla.org/docs/Web/JavaScript

These are, in a way, the required parts of a script but they are by no means the only parts you can have. You can create additional methods as needed - just make sure they are called from somewhere in one of the methods below!





1. System Registration [ edit ]

First off we need to register the system for our file. This signs up our script to be set-up either on the client or server threads of the game. Generally speaking, you will choose based on whether you put the script file in the client or server folders. To do that simply call registerSystem on either the client or server and give it the version of the API you require.

Parameters

Type Name Description Integer majorVersion This is the major version of the Minecraft Script Engine your script was designed to work with Integer minorVersion This is the revision of the Minecraft Script Engine your script was designed to work with

Code Examples

Client System

let sampleClientSystem = client . registerSystem ( 0 , 0 );

Server System

let sampleServerSystem = server . registerSystem ( 0 , 0 );





2. System Initialization [ edit ]

This is the first method that gets called immediately after the system is registered. It will run as soon as the script loads at world start.

You can use this to set up the environment for your script: register custom components and events, sign up event listeners, etc. This will run BEFORE the world is ready and the player has been added to it. This function should be used to initialize variables and setup event listeners.

You shouldn't try to spawn or interact with any entities at this point! You should also avoid interaction with UI elements or sending messages to the chat window since this is called before the player is ready.

Code Example

sampleSystem . initialize = function () { //register event data, register components, register queries, listen for events };





This method gets called once every game tick. The server and client tick at 20 times per second. This is a good place to get, check, and react to component changes.

Code Example

sampleSystem . update = function () { //Update all the things };





4. System Shutdown [ edit ]

This method gets called when the Minecraft Script Engine is shutting down. For the client this is when they leave the world; for the server this is after the last player has exited the world.

Code Example

sampleSystem . shutdown = function () { //Cleanup script only things };

Debugging [ edit ]

Your script isn't working or doing what you want it to do? Fret not! We have built some debugging capabilities into the Script Engine to help you figure out what's going on with your script. If you are new to programming or want to learn more about debugging we suggest checking out the documentation about debugging with Visual Studio available here: https://docs.microsoft.com/visualstudio/debugger

There are two ways to tell what happened when something goes wrong with a script: in-game and advanced, which we will describe below. You only need the game and your script to debug in-game, but you will need a Windows 10 PC and Visual Studio installed for the advanced debugging.





When running a script in-game, the game will automatically print out the message "Something went wrong..." upon reaching an error. You can enable much more descriptive debugging information to be printed to the chat by sending a minecraft:script_logger_config event in the script's System.initialize hook:

sampleSystem . initialize = function () { var scriptLoggerConfig = this . createEventData ( "minecraft:script_logger_config" ); scriptLoggerConfig . data . log_errors = true ; scriptLoggerConfig . data . log_information = true ; scriptLoggerConfig . data . log_warnings = true ; this . broadcastEvent ( "minecraft:script_logger_config" , scriptLoggerConfig ); /* Your other setup operations afterwards */ };

When you run the script in the game, the Script Engine will print out error messages whenever something goes wrong. For example, if you try to get a component that the script engine doesn't know about you will get an error.



To look at these messages you can open the chat screen which will have all the generated error messages there; or you can open the log file that the game generated. The location of the log file varies by platform. On Windows 10 you can find the log file in %APPDATA%\..\Local\Packages\Microsoft.MinecraftUWP_8wekyb3d8bbwe\LocalState\logs

We strongly encourage you to build further debug messages and tools into your scripts while working on them. This will help you discern when something isn't working quite right. Reach out on the official Discord channel if you need additional help: https://discord.gg/Minecraft





If you have a Windows 10 PC with Visual Studio installed, you can attach the Visual Studio debugger and debug your script in real-time.

If you installed Visual Studio with the components mentioned in the "Recommended" section of this document you will have installed and enabled the Just-In-Time Debugger. This tool will pop-up a message from Visual Studio whenever an exception occurs in your script and allow you to open Visual Studio on the line of your script that broke.

Additionally, you can connect to the Script Engine manually and debug your code. You can use remote debugging to connect and debug Minecraft running on another device. Please refer to the Visual Studio Debugger documentation above for instructions on how to use remote debugging.

First you need to start up Visual Studio. If this is the first time you have launched Visual Studio after installation, we suggest setting up your environment for JavaScript development and logging in to your Microsoft account when prompted. This will set up the Visual Studio interface with the most important tools you will need.

Once you have Visual Studio open you should launch Minecraft. Then create a new world with Experimental Gameplay enabled and apply the Behavior Pack containing your scripts.

After creating the world go back to Visual Studio and click on the Debug menu. Then click on "Attach to Process". In the window that opens there will be a search box titled Filter Process. Click on it and type Minecraft.

Once the list is narrowed down to only the instance of Minecraft running, you can verify that the Script Engine is running by looking at the Type column. This will say Script and either x86 or x64.

Select the process and click on Attach to attach the debugger to the game. Now you will be able to press the Pause button to pause the Script Engine when the next line of script code runs. This allows you to inspect the values of variables in your script and break into Visual Studio if an error occurs in your code.

WARNING: When you hit a breakpoint to step through code with a debugger, it is possible for a client to time out and disconnect or for the server to disconnect all players.

Script API Objects [ edit ]

Here you can find the definition of some objects returned by the script API.

Entity JS API Object [ edit ]

Type Name Entity JS API Object Description String __type__ READ ONLY. This defines the type of object. Can be: "entity" or "item_entity". String __identifier__ READ ONLY. This is the identifier for the object in the format namespace:name. For example, if the type is entity and the object is representing a vanilla cow, the identifier would be minecraft:cow Positive Integer id READ ONLY. This is the unique identifier of the entity.

Level JS API Object [ edit ]

Type Name Level JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "level". Positive Integer level_id READ ONLY. This is the unique identifier of the level.

Component JS API Object [ edit ]

Type Name Component JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "component". String __identifier__ READ ONLY. This is the identifier for the object in the format namespace:name. For example, if the component represents the position of an entity the identifier would be minecraft:position. Custom components can also be registered using the same format and with a namespace anything other than minecraft (see: registerComponent()). JavaScript Object data This is the content of the component.

Query JS API Object [ edit ]

Type Name Query JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "query". Positive Integer query_id READ ONLY. This is the unique identifier of the query.

ItemStack JS API Object [ edit ]

Type Name ItemStack JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "item_stack". String __identifier__ READ ONLY. This is the identifier for the object in the format namespace:name. For example, if the type is entity and the object is representing a vanilla cow, the identifier would be minecraft:cow String item READ ONLY. This is the identifier of the item. String count READ ONLY. This is the number of items in the stack.

Block JS API Object [ edit ]

Type Name Block JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "block". String __identifier__ READ ONLY. This is the identifier for the object in the format namespace:name. For example, if the type is block and the object is representing a block of bedrock, the identifier would be minecraft:bedrock JavaScript Object ticking_area READ ONLY. This is the ticking area object that was used to get this block. JavaScript Object block_position READ ONLY. This is the position of the block and it functions as part of its unique identifier. Parameters Type Name Description Integer x The x position Integer y The y position Integer z The z position

Ticking Area JS API Object [ edit ]

There are two types of ticking area objects. Entity and Level. When a function calls for a ticking area it can take either type as an argument.

Entity Ticking Area JS API Object [ edit ]

Type Name Entity Ticking Area JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "entity_ticking_area". Positive Integer entity_ticking_area_id READ ONLY. This is the unique identifier of the ticking area.

Level Ticking Area JS API Object [ edit ]

Type Name Level Ticking Area JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "level_ticking_area". String level_ticking_area_id READ ONLY. This is the unique identifier of the ticking area.

Script Bindings [ edit ]

Bindings are the capabilities of the Minecraft Script Engine to change or modify things in the game.

Entity Bindings [ edit ]

Creates an empty entity with no components and does not place it in the world. The empty entity will be of type custom and have a blank identifier. This is NOT a valid entity that exists in the world, just an empty one that only scripts know about.

NOTE: Entities are created first on the server, with the client notified of new entities afterwards. Be aware that if you send the result object to the client right away, the created entity might not exist on the client yet.

Return Value

Type Value Description Entity JS API Object object An object representing the newly created entity JavaScript Object null Something went wrong when creating the entity





Creates an entity and applies the specified template as defined in JSON. This allows you to quickly create an entity from the applied Behavior Packs as the base for an entity created in scripting. The entity will be spawned into the world with all the components, component groups, and event triggers that are defined in the JSON file of the identifier specified. Only works on scripts registered on the server.

NOTE: Entities are created first on the server, with the client notified of new entities afterwards. Be aware that if you send the result object to the client right away, the created entity might not exist on the client yet.

Parameters

Type Name Description String Type Specifies the type of the entity that is being created by the template. Valid inputs are `entity` and `item_entity` String TemplateIdentifier This can be any of the entity identifiers from the applied Behavior Packs. For example, specifying minecraft:cow here will make the provided entity a cow as defined in JSON





Return Value

Type Value Description Entity JS API Object object An object representing the newly created entity JavaScript Object null Something went wrong when creating the entity





Destroys an entity identified by the EntityObject. If the entity exists in the world this will remove it from the world and destroy it. This also makes the EntityObject no longer valid - you should only destroy an entity after you are done with it and no longer need to reference it again. This does NOT kill the entity. There won't be an event for its death: it will be removed.

Parameters

Type Name Description Entity JS API Object EntityObject The object that was retrieved from a call to createEntity() or retrieved from an entity event





Return Value

Type Value Description Boolean true The entity was successfully destroyed JavaScript Object null Something went wrong when destroying the entity





Checks if the given EntityObject corresponds to a valid entity.

Parameters

Type Name Description Entity JS API Object EntityObject The object that was retrieved from a call to createEntity() or retrieved from an entity event





Return Value

Type Value Description Boolean true The entity is in the Script Engine's database of entities Boolean false The entity is not in the Script Engine's database of entities JavaScript Object null Something went wrong when validating the entity

Component Bindings [ edit ]

Creates a custom component that only exists in script. It can be then added, removed, and updated from entities. These custom components only exist while the Script Engine is running.

Parameters

Type Name Description String ComponentIdentifier The identifier of the custom component. It is required to use a namespace so you can uniquely refer to it later without overlapping a name with a built-in component: for example myPack:myCustomComponent JavaScript Object ComponentData A JavaScript Object that defines the name of the fields and the data each field holds inside the component.





Return Value

Type Value Description Boolean true The component was successfully registered JavaScript Object null Something went wrong when registering the component





Creates the specified component and adds it to the entity. This should only be used with custom components which need to be registered first. If the entity already has the component, this will retrieve the component already there instead.

Parameters

Type Name Description Entity JS API Object EntityObject The EntityObject that was retrieved from a call to createEntity() or retrieved from an event String ComponentIdentifier The identifier of the component to add to the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()





Return Value

Type Value Description Component JS API Object object An object with the following fields, and additionally, all the fields as defined in the component JavaScript Object null Something went wrong when creating the component





Checks if the given entity has the specified component.

Parameters

Type Name Description Entity JS API Object EntityObject The EntityObject that was retrieved from a call to createEntity() or retrieved from an event String ComponentIdentifier The identifier of the component to check on the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()





Return Value

Type Value Description Boolean true The EntityObject has the component Boolean false The EntityObject doesn't have the component JavaScript Object null An unknown component was passed in or something else went wrong when checking if the EntityObject had the component





Looks for the specified component in the entity. If it exists, retrieves the data from the component and returns it.

Parameters

Type Name Description Entity JS API Object EntityObject The EntityObject that was retrieved from a call to createEntity() or retrieved from an event String ComponentIdentifier The identifier of the component to retrieve from the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()





Return Value

Type Value Description Component JS API Object object An object with the following fields, and additionally, all the fields as defined in the component Component JS API Object Type Name Component JS API Object Description String __type__ READ ONLY. This defines the type of object. Will be: "component". JavaScript Object data This is the content of the component. JavaScript Object null The entity did not have the component or something went wrong when getting the component





Applies the component and any changes made to it in script back to the entity. What this means for each component can be slightly different: it makes the component reload on the entity with the new data as if it had just been added to the entity.

Parameters

Type Name Description Entity JS API Object EntityObject The entity object that we are applying the component changes to Component JS API Object ComponentObject The component object retrieved from the entity that was returned by either createComponent() or getComponent()





Return Value

Type Value Description Boolean true The component was successfully updated JavaScript Object null Something went wrong when updating the component





Removes the specified component from the given entity. If the entity has the component, it will be removed. Currently this only works with custom components and can't be used to remove components defined for an entity in JSON.

Parameters

Type Name Description Entity JS API Object EntityObject The EntityObject that was retrieved from a call to createEntity() or retrieved from an event String ComponentIdentifier The identifier of the component to remove from the entity. This is either the identifier of a built-in component (check the Script Components section) or a custom component created with a call to registerComponent()





Return Value

Type Value Description Boolean true The component was successfully removed from the entity JavaScript Object null The entity did not have the component or something went wrong when removing the component

Event Bindings [ edit ]

These are the bindings used to handle events. For a list of events you can react to or trigger, check the Events section of this document.

Registers the Event to the script engine. This allows you to create Event Data by calling createEventData and have it initialized with the correct default data and fields. Only custom events need to be registered.



Parameters

Type Name Description String EventIdentifier This is the identifier of the custom event we are registering. The namespace is required and can't be set to minecraft. JavaScript Object EventData The JavaScript object with the correct fields and default values for the event





Return Value

Type Value Description Boolean true Successfully registered the event data JavaScript Object null Something went wrong when registering the event for listening





Creates an object with all the required fields and default data for the specified event. If the event is a custom event, it needs to have been previously registered.

Parameters

Type Name Description String EventIdentifier This is the identifier of the custom event we are registering. The namespace is required and can't be set to minecraft.





Return Value

Type Value Description JavaScript Object The object containing the event data JavaScript Object null Something went wrong when registering the event for listening





Allows you to register a JavaScript object that gets called whenever the specified event is broadcast. The event can either be a built-in event or an event specified in script.

Parameters

Type Name Description String EventIdentifier This is the identifier of the event to which we want to react. Can be the identifier of a built-in event or a custom one from script JavaScript Object CallbackObject The JavaScript object that will get called whenever the event is broadcast





Return Value

Type Value Description Boolean true Successfully registered to listen for the event JavaScript Object null Something went wrong when registering the event for listening





Allows you to trigger an event with the desired data from script. Anything that signed up to listen for the event will be notified and the given data delivered to them.

Parameters

Type Name Description String EventIdentifier This is the identifier of the event we want to react to. Can be the identifier of a built-in event or a custom one from script JavaScript Object EventData The data for the event. You can create a new JavaScript Object with the parameters you want to pass in to the listener and the engine will take care of delivering the data to them





Return Value

Type Value Description Boolean true Successfully broadcasted the event JavaScript Object null Something went wrong when broadcasting the event

Entity Queries [ edit ]

Entity Queries are a way for you to filter for entities based on their components. Once you have registered a query, you can request all the entities that are captured by it. Entity Queries will only ever return entities that are currently active in the level. If your query extends into chunks that are not currently loaded, entities there will not be included in the query.

Allows you to register a query. A query will contain all entities that meet the filter requirement.

No filters are added by default when you register a query so it will capture all entities.

Return Value

Type Value Description Query JS API Object object An object containing the ID of the query JavaScript Object null Something went wrong when creating the query

Code Example

Query Registration

var simple_query = {}; system . initialize = function () { simple_query = this . registerQuery (); };





Allows you to register a query that will only show entities that have the given component and define which fields of that component will be used as a filter when getting the entities from the query. You can either provide just the component identifier, or the component identifier and the name of 3 properties on that component to be tested (If you do specify property names, you must specify 3).

Parameters

Type Name Default Value Description String Component This is the identifier of the component that will be used to filter entities when String ComponentField1 "x" This is the name of the first field of the component that we want to filter entities by. By default this is set to x. String ComponentField2 "y" This is the name of the second field of the component that we want to filter entities by. By default this is set to y. String ComponentField3 "z" This is the name of the third field of the component that we want to filter entities by. By default this is set to z.





Return Value

Type Value Description Query JS API Object object An object containing the ID of the query JavaScript Object null Something went wrong when creating the query





Code Example

Query Registration

var spacial_query = {}; system . initialize = function () { spacial_query = this . registerQuery ( "minecraft:position" , "x" , "y" , "z" ); };





By default no filters are added. This will allow queries to capture all entities.

Parameters

Type Name Description Query JS API Object Query The object containing the ID of the query that you want to apply the filter to String ComponentIdentifier This is the identifier of the component that will be added to the filter list. Only entities that have that component will be listed in the query

Code Example

Query Filtering

var filtered_query = {}; system . initialize = function () { filtered_query = this . registerQuery (); this . addFilterToQuery ( filtered_query , "minecraft:explode" ); };





Allows you to fetch the entities captured by a query.

Parameters

Type Name Description Query JS API Object Query This is the query you registered earlier using registerQuery()





Return Value

Type Value Description Array array An array of EntityObjects representing the entities found within the query JavaScript Object null Something went wrong when creating the entity





Code Example

Entity Fetching

system . update = function () { let all_entities = this . getEntitiesFromQuery ( simple_query ); let exploding_creepers = this . getEntitiesFromQuery ( filtered_query ); };





Allows you to fetch the entities captured by a query that was created with a component filter built-in. The only entities that will be returned are those entities that have the component that was defined when the query was registered and that have a value in the three fields on that component that were defined in the query within the values specified in the call to getEntitiesFromQuery.

Parameters

Type Name Description Query JS API Object Query This is the query you created earlier using registerQuery(...) Decimal ComponentField1_Min The minimum value that the first component field needs to be on an entity for that entity to be included in the query Decimal ComponentField2_Min The minimum value that the second component field needs to be on an entity for that entity to be included in the query Decimal ComponentField3_Min The minimum value that the third component field needs to be on an entity for that entity to be included in the query Decimal ComponentField1_Max The maximum value that the first component field needs to be on an entity for that entity to be included in the query Decimal ComponentField2_Max The maximum value that the second component field needs to be on an entity for that entity to be included in the query Decimal ComponentField3_Max The maximum value that the third component field needs to be on an entity for that entity to be included in the query





Return Value

Type Value Description Array array An array of EntityObjects representing the entities found within the query JavaScript Object null Something went wrong when creating the entity





Code Example

Entity Fetching

system . update = function () { let player_pos_component = this . getComponent ( player , "minecraft:position" ); let pos = player_pos_component . data ; let entities_near_player = this . getEntitiesFromQuery ( spacial_query , pos . x - 10 , pos . x + 10 , pos . y - 10 , pos . y + 10 , pos . z - 10 , pos . z + 10 ); };

Slash Commands [ edit ]

You can use the traditional Slash Command system from scripts. Currently you can either trigger an event ("minecraft:execute_command") or use the executeCommand binding. Commands in scripts are restricted to server scripts, they can't be run from the client's side at the moment.

Allows you to execute a Slash Command on the server. The command will be queried and executed at the end of the current frame. All data output from the command will be compiled on a JavaScript Object and sent to the Callback object specified in the second parameter.

Parameters

Type Name Description String Command The slash command to run JSON Object Callback The JavaScript object that will be called after the command executes

Example

system . executeCommand ( "/fill ~ ~ ~ ~100 ~5 ~50 stone" , ( commandResultData ) => this . commandCallback ( commandResultData )); system . commandCallback = function ( commandResultData ) { let eventData = this . createEventData ( "minecraft:display_chat_event" ); if ( eventData ) { eventData . data . message = "Callback called! Command: " + commandResultData . command + " Data: " + JSON . stringify ( commandResultData . data , null , " " ); this . broadcastEvent ( "minecraft:display_chat_event" , eventData ); } };

Block Bindings [ edit ]

These functions define how you interact with blocks.

Allows you to get a block from the world when provided an x, y, and z position. The block must be within a ticking area.

Parameters

Type Name Description Ticking Area JS API Object Ticking Area The ticking area the block is in Integer x The x position of the block you want Integer y The y position of the block you want Integer z The z position of the block you want





Return Value

Type Value Description Block JS API Object object An object containing the block JavaScript Object null Something went wrong when retrieving the block





Allows you to get a block from the world when provided a JavaScript object containing a position. The block must be within a ticking area.

Parameters

Type Name Description Ticking Area JS API Object Ticking Area The ticking area the block is in JavaScript Object PositionObject A JavaScript object with the x, y, and z position of the block you want Parameters Type Name Description Integer x The x position Integer y The y position Integer z The z position





Return Value

Type Value Description Block JS API Object object An object containing the block JavaScript Object null Something went wrong when retrieving the block





getBlocks(Ticking Area, x min, y min, z min, x max, y max, z max) [ edit ]

Allows you to get an array of blocks from the world when provided a minimum and maximum x, y, and z position. The blocks must be within a ticking area.

Parameters

Type Name Description Ticking Area JS API Object Ticking Area The ticking area the blocks are in Integer x min The minimum x position of the blocks you want Integer y min The minimum y position of the blocks you want Integer z min The minimum z position of the blocks you want Integer x max The maximum x position of the blocks you want Integer y max The maximum y position of the blocks you want Integer z max The maximum z position of the blocks you want





Return Value

Type Value Description Array array A 3D array of block objects. Indexs are the blocks positions relative to the min position given JavaScript Object null Something went wrong when retrieving the blocks





getBlocks(Ticking Area, Minimum PositionObject, Maximum PositionObject) [ edit ]

Allows you to get an array of blocks from the world when provided a minimum and maximum position. The blocks must be within a ticking area.

Parameters

Type Name Description Ticking Area JS API Object Ticking Area The ticking area the blocks are in JavaScript Object Minimum PositionObject A JavaScript object with the minimum x, y, and z position of the blocks you want Parameters Type Name Description Integer x The x position Integer y The y position Integer z The z position JavaScript Object Maximum PositionObject A JavaScript object with the maximum x, y, and z position of the blocks you want Parameters Type Name Description Integer x The x position Integer y The y position Integer z The z position





Return Value

Type Value Description Array array A 3D array of block objects. Indexs are the blocks positions relative to the min position given JavaScript Object null Something went wrong when retrieving the blocks

Script Components [ edit ]

This is the documentation for the attributes, properties, and components available from the Minecraft Script Engine.

There are two kinds of components: server components and client components. We will go into a bit more detail on what they are in their respective sections below.

Components can be added, retrieved, updated, and removed from entities. They do not exist on their own. Currently only user-defined components can be added and removed from entities. A component must be in an entity in order to retrieve or update it.

Check the Script Engine Bindings section to see how to add, remove, retrieve, and update components. This section deals with the specific API of each component.

Level Components [ edit ]

These are the components that belong to the level. They can only belong on the level object and cannot be removed from it. You can get the components and change their data through the global server object.

let levelComponent = this . getComponent ( server . level , "minecraft:example_level_component" );

This component gives access to the static ticking areas in the level. The component contains an array of ticking areas. The ticking areas can be accessed by name or by UUID if they were not given a name.

The weather component allows users to change the level's weather. Rain and lightning levels can be changed independently and the default weather cycle can be turned off completely.

Parameters

Type Name Description Boolean do_weather_cycle This is the world option that determines if the vanilla weather cycle will be used Decimal rain_level A value between 0 and 1 that determains how heavy the rainfall is Integer rain_time How long, in ticks, it will rain for Decimal lightning_level A value between 0 and 1 that determines how much lightning and thunder there is Integer lightning_time How long, in ticks, it will lightning and thunder for

Server Components [ edit ]

These are the components that run on the server and are synced with all the clients (players) in the world.

As much as possible, the API of each component matches its JSON counterpart (with some differences noted).

This component represents the armor contents of an entity. The component contains an array of ItemStack JS API Objects representing each slot in the armor container.

NOTE: Currently items and containers are read-only. Slots are ordered from head to feet.

// This example will check the players helmet armor slot for a specific item after the player attacks an entity. system . listenForEvent ( "minecraft:player_attacked_entity" , function ( eventData ) { // Get the players armor container let playerArmor = system . getComponent ( eventData . data . player , "minecraft:armor_container" ); // Get the players helmet let playerHelmet = playerArmor . data [ 0 ]; // Destroy the attacked entity if the player has a gold helmet equipped if ( playerHelmet . item ==== "minecraft:golden_helmet" ) { system . destroyEntity ( eventData . data . attacked_entity ); } });

This component controls the Attack Damage attribute from the entity. It allows you to change the current minimum and maximum values. Once the changes are applied, the current attack of the entity will be reset to the minimum specified. With the minimum and maximum changed to the values specified. Any buffs or debuffs will be left intact.

Parameters

Type Name Default Value Description Range [a, b] damage Range of the random amount of damage the melee attack deals. A negative value can heal the entity instead of hurting it Parameters Type Name Default Value Description Decimal range_min 0.0 The minimum amount of damage the entity will deal Decimal range_max 0.0 The maximum amount of damage the entity will deal

Controls the collision box of the entity. When changes to the component are applied the entity's collision box is immediately updated to reflect the new dimensions.

WARNING: If the change of the collision box dimensions would cause the entity to be inside a block, the entity might become stuck there and start suffocating.

Parameters

Type Name Default Value Description Decimal width 1.0 Width and Depth of the collision box in blocks. A negative value will be assumed to be 0 Decimal height 1.0 Height of the collision box in blocks. A negative value will be assumed to be 0

Defines an array of damages and how the entity reacts to them - including whether the entity ignores that damage or not. Currently Minecraft triggers can't be properly serialized so any existing triggers will be completely replaced when applyComponentChanges().

Parameters

Type Name Default Value Description List on_damage List of triggers with the events to call when taking this specific kind of damage, allows specifying filters for entity definitions and events Boolean deals_damage true If true, the damage dealt to the entity will take away health from it, set to false to make the entity ignore that damage String cause Type of damage that triggers this set of events

// This example will cause an entity (in this case, a creeper) to start exploding when the player attacks it. // Note: the entity must have the damage_sensor component and the associated events defined in their JSON description. this . listenForEvent ( "minecraft:player_attacked_entity" , function ( eventData ) { let damageSensorComponent = serverSystem . getComponent ( eventData . attacked_entity , "minecraft:damage_sensor" ); damageSensorComponent . data [ 0 ]. on_damage = { event : "minecraft:start_exploding" , filters : [{ test : "has_component" , operator : "==" , value : "minecraft:breathable" }] }; serverSystem . applyComponentChanges ( eventData . attacked_entity , damageSensorComponent ); });

Defines the loot table the entity uses to defines its equipment. Once the changes are applied, the equipment is re-rolled and a new set of equipment is chosen for the entity.

Parameters

Type Name Default Value Description String table The file path to the equipment table, relative to the behavior pack's root List slot_drop_chance A list of slots with the chance to drop an equipped item from that slot

Defines how many and what items the entity can be equipped with.

slots

List of slots and the item that can be equipped.

Parameters

Type Name Default Value Description Integer slot 0 The slot number of this slot List accepted_items The list of items that can go in this slot String item Identifier of the item that can be equipped for this slot String interact_text Text to be displayed when the entity can be equipped with this item when playing with Touch-screen controls String on_equip Event to trigger when this entity is equipped with this item String on_unequip Event to trigger when this item is removed from this entity

Controls the entity's explosion, timer until the explosion, and whether the timer is counting down or not.

Parameters

Type Name Default Value Description Range [a, b] fuseLength [0.0, 0.0] The range for the random amount of time the fuse will be lit before exploding, a negative value means the explosion will be immediate Decimal power 3.0 The radius of the explosion in blocks and the amount of damage the explosion deals Decimal maxResistance Infinite A blocks explosion resistance will be capped at this value when an explosion occurs Boolean fuseLit false If true, the fuse is already lit when this component is added to the entity Boolean causesFire false If true, blocks in the explosion radius will be set on fire Boolean breaks_blocks true If true, the explosion will destroy blocks in the explosion radius Boolean fireAffectedByGriefing false If true, whether the explosion causes fire is affected by the mob griefing game rule Boolean destroyAffectedByGriefing false If true, whether the explosion breaks blocks is affected by the mob griefing game rule

This component represents the contents of an entity's hands. The component contains an array of ItemStack JS API Objects representing each slot in the hand container.

Note: Currently items and containers are read-only. Slot 0 is main-hand Slot 1 is off-hand.

// This example will check the players offhand slot for a specific item after the player attacks an entity. system . listenForEvent ( "minecraft:player_attacked_entity" , function ( eventData ) { // Get the players hand container let handContainer = system . getComponent ( eventData . data . player , "minecraft:hand_container" ); // Get the players offhand item let offhandItem = handContainer . data [ 1 ]; // Destroy the attacked entity if the player has a totem in their offhand if ( offhandItem . item ==== "minecraft:totem" ) { system . destroyEntity ( eventData . data . attacked_entity ); } });

Defines how the entity can be healed by the player. This doesn't control how much health the entity can have; you must use the Health component for that instead.

Parameters

Type Name Default Value Description Array items The array of items that can be used to heal this entity Parameters Type Name Default Value Description String item Item identifier that can be used to heal this entity Integer heal_amount 1 The amount of health this entity gains when fed this item Minecraft Filter filters The filter group that defines the conditions for using this item to heal the entity Boolean force_use false Determines if item can be used regardless of entity being at full health Minecraft Filter filters The filter group that defines the conditions for this trigger

Defines the current and maximum possible health of the entity. Upon applying the component back to the entity the health will change. If it reaches 0 or below the entity will die.

Parameters

Type Name Default Value Description Integer value 1 Current health of the entity Integer max 10 The maximum health the entity can heal

This component represents the hotbar contents of a player. The component contains an array of ItemStack JS API Objects representing each slot in the hotbar.

NOTE: Currently items and containers are read-only. Slots are ordered left to right.

// This example will check the players first hotbar item slot for a specific item after the player attacks an entity. system . listenForEvent ( "minecraft:player_attacked_entity" , function ( eventData ) { // Get the players hotbar let playerHotbar = system . getComponent ( eventData . data . player , "minecraft:hotbar_container" ); // Get the item at the first slot in the hotbar let firstHotbarSlot = playerHotbar . data [ 0 ]; // Destroy the attacked entity if the player has an apple in their first hotbar slot if ( firstHotbarSlot . item ==== "minecraft:apple" ) { system . destroyEntity ( eventData . data . attacked_entity ); } });

Defines the ways the player can interact with the entity to which this component is applied.

Parameters

Type Name Default Value Description Array spawn_entities An array of entity identifiers to spawn when the interaction occurs String on_interact An event identifier to fire when the interaction occurs JSON Object particle_on_start Particle effect that will be triggered at the start of the interaction Parameters Type Name Default Value Description String particle_type The type of particle that will be spawned Decimal particle_y_offset 0.0 Will offset the particle this amount in the y direction Boolean particle_offset_towards_interactor false Whether or not the particle will appear closer to who performed the interaction Decimal cooldown 0.0 Time in seconds before this entity can be interacted with again Boolean swing false If true, the player will do the 'swing' animation when interacting with this entity Boolean use_item false If true, the interaction will use an item Integer hurt_item 0 The amount of damage the item will take when used to interact with this entity. A value of 0 means the item won't lose durability String interact_text Text to show when the player is able to interact in this way with this entity when playing with Touch-screen controls JSON Object add_items Loot table with items to add to the player's inventory upon successful interaction Parameters Type Name Default Value Description String table File path, relative to the behavior pack's path, to the loot table file JSON Object spawn_items Loot table with items to drop on the ground upon successful interaction Parameters Type Name Default Value Description String table File path, relative to the behavior pack's path, to the loot table file String transform_to_item The item used will transform to this item upon successful interaction. Format: itemName:auxValue Array play_sounds An array of sound identifiers to play when the interaction occurs

Defines the entity's inventory (size, restrictions, etc.). Currently this does not allow changing the entity's inventory contents.

Parameters

Type Name Default Value Description String container_type none Type of container this entity has. Can be horse, minecart_chest, minecart_hopper, inventory, container or hopper Integer inventory_size 5 Number of slots the container has Boolean can_be_siphoned_from false If true, the contents of this inventory can be removed by a hopper Boolean private false If true, only the entity can access the inventory Boolean restrict_to_owner false If true, the entity's inventory can only be accessed by its owner or itself Integer additional_slots_per_strength 0 Number of slots that this entity can gain per extra strength





This component represents the inventory contents of an entity. The component contains an array of ItemStack JS API Objects representing each slot in the inventory. NOTE: Currently items and containers are read-only.Slot 0-8 is the hotbar, 9-17 is the top row of the player's inventory, 18-26 is the middle row, 27-35 is the bottom row

// This example will check the players third inventory item slot for a specific item after the player attacks an entity. system . listenForEvent ( "minecraft:player_attacked_entity" , function ( eventData ) { // Get the players inventory let playerInventory = system . getComponent ( eventData . data . player , "minecraft:inventory_container" ); // Get the item at the third slot in the inventory let thirdItemSlot = playerInventory . data [ 2 ]; // Destroy the attacked entity if the player has an apple in their third item slot if ( thirdItemSlot . item ==== "minecraft:apple" ) { system . destroyEntity ( eventData . data . attacked_entity ); } });

Makes the entity look at another entity. Once applied, if an entity of the specified type is nearby and can be targeted the entity will turn towards it.

Parameters

Type Name Default Value Description Boolean setTarget true If true, this entity will set the attack target as the entity that looked at it Decimal searchRadius 10.0 Maximum distance this entity will look for another entity looking at it Boolean mAllowInvulnerable false If true, invulnerable entities (e.g. Players in creative mode) are considered valid targets Range [a, b] look_cooldown [0.0, 0.0] The range for the random amount of time during which the entity is 'cooling down' and won't get angered or look for a target Minecraft Filter filters player Defines the entities that can trigger this component String look_event The event identifier to run when the entities specified in filters look at this entity





Nameable component describes an entity's ability to be named using a nametag and whether the name shows up or not once applied. Additionally, scripting allows setting the name of the entity directly with the property 'name'.

Parameters

Type Name Default Value Description JSON Object name_actions Describes the special names for this entity and the events to call when the entity acquires those names Parameters Type Name Default Value Description String on_named Event to be called when this entity acquires the name specified in 'name_filter' List name_filter List of special names that will cause the events defined in 'on_named' to fire String default_trigger Trigger to run when the entity gets named Boolean alwaysShow false If true, the name will always be shown Boolean allowNameTagRenaming true If true, this entity can be renamed with name tags String name The current name of the entity, empty if the entity hasn't been named yet, making this non-empty will apply the name to the entity

This component allows you to control an entity's current position in the world. Once applied the entity will be teleported to the new position specified.

Parameters

Type Name Default Value Description Decimal x 0.0 Position along the X-Axis (east-west) of the entity Decimal y 0.0 Position along the Y-Axis (height) of the entity Decimal z 0.0 Position along the Z-Axis (north-south) of the entity

This component allows you to control an entity's current rotation in the world as well as the entity's head rotation. Once applied, the entity will be rotated as specified.

Parameters

Type Name Default Value Description Decimal x 0.0 Controls the head rotation looking up and down Decimal y 0.0 Controls the body rotation parallel to the floor

Defines the entity's ranged attacks. This doesn't allow the entity to use a ranged attack: it only defines what kind of projectile it shoots.

Parameters

Type Name Default Value Description String def Entity identifier to use as projectile for the ranged attack. The entity must have the projectile component to be able to be shot as a projectile Integer auxVal -1 ID of the Potion effect to be applied on hit

Controls the entity's ability to spawn an entity or an item. This is similar to the chicken's ability to lay eggs after a set amount of time.

Parameters

Type Name Default Value Description Boolean should_leash false If true, this the spawned entity will be leashed to the parent Integer num_to_spawn 1 The number of entities of this type to spawn each time that this triggers Integer min_wait_time 300 Minimum amount of time to randomly wait in seconds before another entity is spawned Integer max_wait_time 600 Maximum amount of time to randomly wait in seconds before another entity is spawned String spawn_sound plop Identifier of the sound effect to play when the entity is spawned String spawn_item egg Item identifier of the item to spawn String spawn_entity Identifier of the entity to spawn, leave empty to spawn the item defined above instead String spawn_method born Method to use to spawn the entity String spawn_event minecraft:entity_born Event to call when the entity is spawned Minecraft Filter filters If present, the specified entity will only spawn if the filter evaluates to true Boolean single_use false If true, this component will only ever spawn the specified entity once

This controls the entity's ability to teleport itself (similar to the Enderman). If you wish to teleport the entity once use the Position component instead.

Parameters

Type Name Default Value Description Boolean randomTeleports true If true, the entity will teleport randomly Decimal minRandomTeleportTime 0.0 Minimum amount of time in seconds between random teleports Decimal maxRandomTeleportTime 20.0 Maximum amount of time in seconds between random teleports Vector [a, b, c] randomTeleportCube [32.0, 16.0, 32.0] Entity will teleport to a random position within the area defined by this cube Decimal targetDistance 16.0 Maximum distance the entity will teleport when chasing a target Decimal target_teleport_chance 1.0 The chance that the entity will teleport between 0.0 and 1.0. 1.0 means 100% Decimal lightTeleportChance 0.01 Modifies the chance that the entity will teleport if the entity is in daylight Decimal darkTeleportChance 0.01 Modifies the chance that the entity will teleport if the entity is in darkness

The tick world component is a read-only component that allows users to access the ticking areas on entities as well as the ticking area's data.

Parameters

Type Name Description Integer radius The radius in chunks of the ticking area Decimal distance_to_players distance_to_players Boolean never_despawn Whether or not this ticking area will despawn when a player is out of range Entity Ticking Area JS API Object ticking_area The ticking area entity that is attached to this entity

Client Components [ edit ]

These components only run on the client where the script ran and can only be used from client scripts.

The MoLang component gives access to the MoLang variables in an entity. To learn more about MoLang varibles review the add-on documentation. In scripts, you can get and set these varibles that are defined in the entity's JSON files. Because of how the MoLang variables are formatted (variable.isgrazing for example) you must use the [] operator on the object to access the variable. The example below shows how to use the [] operator to access the variable.

Code Example

let molangComponent = this . createComponent ( entity , "minecraft:molang" ); molangComponent [ "variable.molangexample" ] = 1.0 ; this . applyComponentChanges ( molangComponent );

Block Components [ edit ]

These components are only found on block objects and can only be on block objects

This component contains all the blockstates on a block object. Blockstates control all different aspects of blocks from their orientation to the type of wood they are. Blockstates are represented by numbers, bools, or strings. Please see the Blockstates Documentation to see the valid values for each state. This component allows for the getting and setting of these states.

Code Example

let blockstateComponent = this . getComponent ( block , "minecraft:blockstate" ); blockstateComponent . data . coral_color = "blue" ; this . applyComponentChanges ( block , blockstateComponent );

User-Defined Components [ edit ]

User-defined components are a special kind of component that can be defined in script and no built-in game system acts on it.

The component needs to be registered with the Script Engine by giving it a name and a set of fields in the format name:value. Once applied, the component behaves like any of the built-in components: you can get it from an entity, modify its values, and apply the changes.

Currently User-defined components are the only components that can be dynamically added and removed from an entity using scripts. They don't need to be previously defined in an entity's JSON file. In the current version these components will NOT be saved out or loaded back in: they only exist while the entity is there and need to be added back when reloading the level.

Code Example

Component Registration

this . registerComponent ( "myNamespace:myComponent" , { myString : "TamerJeison" , myInt : 42 , myFloat : 1.0 , myArray : [ 1 , 2 , 3 ], myObject : { a : 1 , b : 2 , c : 3 }});

Script Events [ edit ]

Here you can find the list of events that you can listen for and respond to in your scripts.

Client Events [ edit ]

Listening Events [ edit ]

The following Minecraft events are events the Script Engine is listening for and to which you can react in scripts.

This event is fired whenever a player joins the world.

Type Name Description Entity JS API Object player The player that joined

This event is triggered whenever the reticle changes from pointing at a block or air to pointing at an entity and the other way around. Up to 1000 blocks away.

Type Name Description Entity JS API Object entity The entity that was hit or null if it fired when moving off of an entity Vector [a, b, c] position The position of the entity that was hit or null if it fired when moving off an entity

// Code Example system . initialize = function () { this . listenForEvent ( "minecraft:hit_result_changed" , this . onPick . bind ( this )); }; system . onPick = function ( eventData ) { if ( eventData . data . position !== null ) { this . broadcastEvent ( "minecraft:display_chat_event" , "Pick at x:" + eventData . data . position . x + " y:" + eventData . data . position . y + " z:" + eventData . data . position . z ); } };

This event is triggered every update and tells you what entity the reticle is pointing to in the world up to 1000 blocks away.

Type Name Description Entity JS API Object entity The entity that was hit or null if it not pointing at an entity Vector [a, b, c] position The position of the entity that was hit or block that was hit

// Code Example system . initialize = function () { this . listenForEvent ( "minecraft:hit_result_continuous" , this . onPick . bind ( this )); }; system . onPick = function ( eventData ) { if ( eventData . data . position !== null ) { this . broadcastEvent ( "minecraft:display_chat_event" , "Pick at x:" + eventData . data . position . x + " y:" + eventData . data . position . y + " z:" + eventData . data . position . z ); } };

This event is triggered whenever the mouse pointer changes from pointing at a block or air to pointing at an entity and the other way around. Up to 1000 blocks away.

Type Name Description Entity JS API Object entity The entity that was hit or null if it fired when moving off of an entity Vector [a, b, c] position The position of the entity that was hit or null if it fired when moving off an entity

// Code Example system . initialize = function () { this . listenForEvent ( "minecraft:pick_hit_result_changed" , this . onPick . bind ( this )); }; system . onPick = function ( eventData ) { if ( eventData . data . position !== null ) { this . broadcastEvent ( "minecraft:display_chat_event" , "Pick at x:" + eventData . data . position . x + " y:" + eventData . data . position . y + " z:" + eventData . data . position . z ); } };

This event is triggered every update and tells you what entity the mouse pointer is pointing to in the world up to 1000 blocks away.

Type Name Description Entity JS API Object entity The entity that was hit or null if it not pointing at an entity Vector [a, b, c] position The position of the entity that was hit or block that was hit

// Code Example system . initialize = function () { this . listenForEvent ( "minecraft:pick_hit_result_continuous" , this . onPick . bind ( this )); }; system . onPick = function ( eventData ) { if ( eventData . data . position !== null ) { this . broadcastEvent ( "minecraft:display_chat_event" , "Pick at x:" + eventData . data . position . x + " y:" + eventData . data . position . y + " z:" + eventData . data . position . z ); } };

Trigger-able Events [ edit ]

The following Minecraft Events can be triggered from scripting and cause the game to respond accordingly.

// Helper Function /** * Simplifies broadcasting events * @param {string} identifier The event identifier in the format 'namespace:name' * @param {Object} properties The event properties * @returns {(boolean|null)} Returns 'true' if event broadcast was successful or 'null' when event broadcast failed */ system . emit = function ( identifier , properties ) { const data = this . createEventData ( identifier ); data . data = Object . assign ({}, data . data , properties ); return this . broadcastEvent ( identifier , data ); }

This event is used to display a chat message to the specific player that is running the client script. The event data is the message to be displayed in plain text. Special formatting is supported the same way it would be if a player was sending the message.

Type Name Default Value Description String message The chat message that will be displayed

// Helper Function /** * Simplifies logging * @param {...*} items The variables to log */ system . log = function (... items ) { const toString = item => { switch ( Object . prototype . toString . call ( item )) { case '[object Undefined]' : return 'undefined' ; case '[object Null]' : return 'null' ; case '[object String]' : return `" ${ item } "` ; case '[object Array]' : const array = item . map ( toString ); return `[ ${ array . join ( ', ' ) } ]` ; case '[object Object]' : const object = Object . keys ( item ). map ( key => ` ${ key } : ${ toString ( item [ key ]) } ` ); return `{ ${ object . join ( ', ' ) } }` ; case '[object Function]' : return item . toString (); default : return item ; } } this . emit ( 'minecraft:display_chat_event' , { message : items . map ( toString ). join ( ' ' )}); }, // Example const myString = 'Hello' ; const myInt = 5 ; const myObject = { a : undefined , b : 'World' }; system . log ( myString , myInt , myObject ) // Result: <Client Script> "Hello" 5 {a: undefined, b: "World"}

This event is used to show a UI screen to the specific player running the client script. This event will add the UI screen to the top of the UI screen stack. The screen will be shown immediately after the event is triggered. Only screens defined in a HTML file can be shown using this event.

Event Data Parameters

Type Name Default Value Description String path The file path to the screen's HTML file JSON Object options You can define the following options for the screen by setting their value to true or false: always_accepts_input If true, the screen will always accept and process input for as long as it is in the stack, even if other custom UI screens appear on top of it render_game_behind If true, the game will continue to be rendered underneath this screen absorbs_input If true, input will not be passed down to any other screens underneath is_showing_menu If true, the screen will be treated as the pause menu and the pause menu won't be allowed to show on top of this screen should_steal_mouse If true, the screen will capture the mouse pointer and limit its movement to the UI screen force_render_below If true, this screen will be rendered even if another screen is on top of it and will render over them, including the HUD render_only_when_topmost If true, this screen will only be rendered if it is the screen at the top of the stack

This event is used to send UI events to the UI Engine for the specific player running the script. After the event is triggered, the UI event will be sent immediately.

Custom UI is based on HTML 5. Review the scripting demo for an example of a custom UI file.

Type Name Description String eventIdentifier The identifier of the UI event String data The data for the UI event being triggered

This event is used to create a particle effect that will follow an entity around. This particle effect is only visible to the specific player that is running the client script where you fired the event. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. MoLang variables defined in the JSON of the effect can then be used to control that effect by changing them in the entity to which it is attached.

Type Name Default Value Description String effect The identifier of the particle effect you want to attach to the entity. This is the same name you gave the effect in its JSON file Vector [a, b, c] offset [0, 0, 0] The offset from the entity's "center" where you want to spawn the effect Entity JS API Object entity The entity object you want to attach the effect to

This event is used to create a static particle effect in the world. This particle effect is only visible to the specific player that is running the client script where you fired the event. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. Once the effect is spawned you won't be able to control it further. Unlike the server version of the event, the client version will spawn the particle in the dimension the player is currently in.

Type Name Default Value Description String effect The identifier of the particle effect you want to attach to spawn. This is the same name you gave the effect in its JSON file Vector [a, b, c] position [0, 0, 0] The position in the world where you want to spawn the effect

This event is used to remove a UI screen from the stack of the specific player running the client script. The event data contains the name of the screen to remove as a string. After the event is triggered the screen will be scheduled to be removed from the stack the next time the UI Engine can do so. Only screens defined in a HTML file can be removed using this event.

This event is used to turn various levels of logging on and off for client scripts. Note that turning logging on/off is not limited to the script that broadcasted the event. It will affect ALL client scripts including those in other Behavior Packs that are applied to the world. See the Debugging section for more information on logging.

Type Name Default Value Description Boolean log_errors false Set to true to log any scripting errors that occur on the client Boolean log_warnings false Set to true to log any scripting warnings that occur on the client Boolean log_information false Set to true to log any general scripting information that occurs on the client. This includes any logging done with client.log()

Server Events [ edit ]

Listening Events [ edit ]

The following Minecraft events are events the Script Engine is listening for and to which you can react in scripts.

This event is triggered whenever a player attacks an entity.

Type Name Description Entity JS API Object player The player that attacked an entity Entity JS API Object attacked_entity The entity that was attacked by the player

This event is triggered whenever an entity acquires an item.

Type Name Description Entity JS API Object entity The entity who acquired the item ItemStack JS API Object item_stack The item that was acquired String acquisition_method The way the entity acquired the item Integer acquired_amount The total number of items acquired by the entity during this event Entity JS API Object secondary_entity If it exists, the entity that affected the item before it was acquired. Example: A player completes a trade with a villager. The `entity` property would be the player and the `secondary_entity` would be the villager

This event is triggered whenever an entity changes the item carried in their hand.

Type Name Description Entity JS API Object entity The entity that changed what they were carrying ItemStack JS API Object previous_carried_item The item that was previously in the entitie's hand ItemStack JS API Object carried_item The item that is now in the entitie's hand

This event is triggered whenever an entity is added to the world.

Type Name Description Entity JS API Object entity The entity that was just created

This event is triggered whenever an entity dies. This won't be triggered when an entity is removed (such as when using destroyEntity).

Type Name Description Entity JS API Object entity The entity that died

This event is triggered whenever an entity drops an item.

Type Name Description Entity JS API Object entity The entity who dropped the item ItemStack JS API Object item_stack The item that was dropped

This event is triggered whenever an entity equips an item in their armor slots.

Type Name Description Entity JS API Object entity The entity who is equipping the armor ItemStack JS API Object item_stack The armor that is being equipped

This event is triggered whenever an entity becomes a rider on another entity.

Type Name Description Entity JS API Object entity The rider Entity JS API Object ride The entity being ridden

This event is triggered whenever an entity stops riding another entity.

Type Name Description Entity JS API Object entity The entity that was riding another entity Boolean exit_from_rider If true, the rider stopped riding by their own decision Boolean entity_is_being_destroyed If true, the rider stopped riding because they are now dead Boolean switching_rides If true, the rider stopped riding because they are now riding a different entity

This event is triggered whenever an entity is ticked. This event will not fire when a player is ticked.

Type Name Description Entity JS API Object entity The entity that was ticked

This event is triggered whenever an entity uses an item.

Type Name Description Entity JS API Object entity The entity who is using the item ItemStack JS API Object item_stack The item that is being used String use_method The way the entity used the item

This event is triggered whenever a player starts to destroy a block.

Type Name Description Entity JS API Object player The player that started destoying the block JavaScript Object block_position The position of the block that is being destroyed

This event is triggered whenever a player stops destroying a block.

Type Name Description Entity JS API Object player The player that stopped destoying the block JavaScript Object block_position The position of the block that was being destroyed Decimal destruction_progress How far along the destruction was before it was stopped (0 - 1 range)

This event is triggered whenever a player interacts with a block.

Type Name Description Entity JS API Object player The player that interacted with the block JavaScript Object block_position The position of the block that is being interacted with

This event is triggered whenever a piston moves a block.

Type Name Description JavaScript Object piston_position The position of the piston that moved the block JavaScript Object block_position The position of the block that was moved String piston_action The action the piston took, "extended" or "retracted"

This event is triggered whenever a player destroys a block.

Type Name Description Entity JS API Object player The player that destroyed the block JavaScript Object block_position The position of the block that was destroyed String block_identifier The identifier of the block that was destroyed

This event is triggered whenever a player places a block.

Type Name Description Entity JS API Object player The player that placed the block JavaScript Object block_position The position of the block that was placed

This event is used to play a sound effect. Currently, sounds can only be played at a fixed position in the world. Global sounds and sounds played by an entity will be supported in a later update.

Type Name Default Value Description String sound The identifier of the sound you want to play. Only sounds defined in the applied resource packs can be played Decimal volume 1.0 The volume of the sound effect. A value of 1.0 will play the sound effect at the volume it was recorded at Decimal pitch 1.0 The pitch of the sound effect. A value of 1.0 will play the sound effect with regular pitch Vector [x, y, z] position [0, 0, 0] The position in the world we want to play the sound at

This event is triggered whenever the weather changes. It contains information about the weather it is changing to.

Type Name Description String dimension The name of the dimension where the weather change happened Boolean raining Tells if the new weather has rain Boolean lightning Tells if the new weather has lightning





Trigger-able Events [ edit ]

The following Minecraft events can be triggered from scripting and the game will respond, accordingly.

// Helper Function /** * Simplifies broadcasting events * @param {string} identifier The event identifier in the format 'namespace:name' * @param {Object} properties The event properties * @returns {(boolean|null)} Returns 'true' if event broadcast was successful or 'null' when event broadcast failed */ system . emit = function ( identifier , properties ) { const data = this . createEventData ( identifier ); data . data = Object . assign ({}, data . data , properties ); return this . broadcastEvent ( identifier , data ); }

This event is used to send a chat message from the server to the players. The event data's message is sent as a string. Special formatting is supported the same way it would be if a player was sending the message.

Type Name Default Value Description String message The chat message that will be displayed

// Helper Function /** * Simplifies logging * @param {...*} items The variables to log */ system . log = function (... items ) { const toString = item => { switch ( Object . prototype . toString . call ( item )) { case '[object Undefined]' : return 'undefined' ; case '[object Null]' : return 'null' ; case '[object String]' : return `" ${ item } "` ; case '[object Array]' : const array = item . map ( toString ); return `[ ${ array . join ( ', ' ) } ]` ; case '[object Object]' : const object = Object . keys ( item ). map ( key => ` ${ key } : ${ toString ( item [ key ]) } ` ); return `{ ${ object . join ( ', ' ) } }` ; case '[object Function]' : return item . toString (); default : return item ; } } this . emit ( 'minecraft:display_chat_event' , { message : items . map ( toString ). join ( ' ' )}); }, // Example const myString = 'Hello' ; const myInt = 5 ; const myObject = { a : undefined , b : 'World' }; system . log ( myString , myInt , myObject ) // Result: <Server Script> "Hello" 5 {a: undefined, b: "World"}

This event is used to execute a slash command on the server with the World Owner permission level. The event data contains the slash command as a string. The slash command will be processed and will run after the event is sent.

Type Name Default Value Description String command The command that will be run

This event is used to play a sound effect. Currently, sounds can only be played at a fixed position in the world. Global sounds and sounds played by an entity will be supported in a later update.

Type Name Default Value Description String sound The identifier of the sound you want to play. Only sounds defined in the applied resource packs can be played Decimal volume 1.0 The volume of the sound effect. A value of 1.0 will play the sound effect at the volume it was recorded at Decimal pitch 1.0 The pitch of the sound effect. A value of 1.0 will play the sound effect with regular pitch Vector [x, y, z] position [0, 0, 0] The position in the world we want to play the sound at

This event is used to create a particle effect that will follow an entity around. This particle effect is visible to all players. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. MoLang variables defined in the JSON of the effect can then be used to control that effect by changing them in the entity to which it is attached.

Type Name Default Value Description String effect The identifier of the particle effect you want to attach to the entity. This is the same identifier you gave the effect in its JSON file Vector [x, y, z] offset [0, 0, 0] The offset from the entity's "center" where you want to spawn the effect Entity JS API Object entity The entity object you want to attach the effect to

This event is used to create a static particle effect in the world. This particle effect is visible to all players. Any effect defined in a JSON file (both in your resource pack and in Minecraft) can be used here. Once the effect is spawned you won't be able to control it further.

Type Name Default Value Description String effect The identifier of the particle effect you want to attach to spawn. This is the same name you gave the effect in its JSON file Vector [x, y, z] position [0, 0, 0] The position in the world where you want to spawn the effect String dimension overworld The dimension in which you want to spawn the effect. Can be "overworld", "nether", or "the end"

This event is used to turn various levels of logging on and off for server scripts. Note that turning logging on/off is not limited to the script that broadcasted the event. It will affect ALL server scripts including those in other Behavior Packs that are applied to the world. See the Debugging section for more information on logging.