In almost every application that does not use the technique we’ll talk about, we’ll see imports such as the following:

import { forIn } from '../../../../../utils/array'

Yes, it’s part of our routine, but there are three problems with this:

The deeper it gets, the worse it gets. It makes it harder to refactor the code. If we want to extract the code to an npm module so other applications in our company can use it, we’ll have to change the entire codebase.

What if we could just write something like this:

import { forIn } from '@datorama/utils/array'

Actually we can 😍. TypeScript allows the use of path mapping which allows arbitrary module paths (that doesn’t start with “/” or “.”) to be specified and mapped to physical paths in the filesystem.

The TypeScript compiler can resolve these paths from tsconfig so it will compile OK.

Let’s see how we use it.

Use with Angular

If you are working with the angular-cli , you need to add two properties to the main tsconfig.json file.

tsconfig.json

The first property that we must add is the baseUrl property. Notice that paths are resolved relative to baseUrl .

The second property is the paths property. This tells the compiler for any module import that matches the pattern "@datorama/utils/*" , to look in the following location:

<moduleName> => <baseUrl>/utils/<moduleName>

Webstorm Demo

Use with Webpack

If you are working with awesome-typescript-loader you need to add the TsConfigPathsPlugin to your webpack config file.

webpack.config.js

That’s all.

The biggest advantage is that if we want to extract reusable code — like utils, pipes, directives to a private npm module so other projects in our company can use it too — we don’t need to change anything in our codebase. We just need to give the module the same name.

🚀 In Case You Missed It

Akita : One of the leading state management libraries, used in countless production environments. Whether it’s entities arriving from the server or UI state data, Akita has custom-built stores, powerful tools, and tailor-made plugins, which all help to manage the data and negate the need for massive amounts of boilerplate code.

: One of the leading state management libraries, used in countless production environments. Whether it’s entities arriving from the server or UI state data, Akita has custom-built stores, powerful tools, and tailor-made plugins, which all help to manage the data and negate the need for massive amounts of boilerplate code. Spectator : A library that runs as an additional layer on top of the Angular testing framework, that saves you from writing a ton of boilerplate.

: A library that runs as an additional layer on top of the Angular testing framework, that saves you from writing a ton of boilerplate. And of course, Transloco: The Internationalization library Angular 😀

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