This chapter documents all the JavaScript language operators, expressions and keywords.

Expressions and operators by category

For an alphabetical listing see the sidebar on the left.

Primary expressions

Basic keywords and general expressions in JavaScript.

this The this keyword refers to a special property of an execution context. function The function keyword defines a function expression. class The class keyword defines a class expression. function* The function* keyword defines a generator function expression. yield Pause and resume a generator function. yield* Delegate to another generator function or iterable object. async function The async function defines an async function expression. await Pause and resume an async function and wait for the promise's resolution/rejection. [] Array initializer/literal syntax. {} Object initializer/literal syntax. /ab+c/i Regular expression literal syntax. ( ) Grouping operator.

Left-hand-side expressions

Left values are the destination of an assignment.

Property accessors Member operators provide access to a property or method of an object

( object.property and object["property"] ). new The new operator creates an instance of a constructor. new.target In constructors, new.target refers to the constructor that was invoked by new . super The super keyword calls the parent constructor. ...obj Spread syntax allows an expression to be expanded in places where multiple arguments (for function calls) or multiple elements (for array literals) are expected.

Increment and decrement

Postfix/prefix increment and postfix/prefix decrement operators.

A++ Postfix increment operator. A-- Postfix decrement operator. ++A Prefix increment operator. --A Prefix decrement operator.

Unary operators

A unary operation is operation with only one operand.

delete The delete operator deletes a property from an object. void The void operator discards an expression's return value. typeof The typeof operator determines the type of a given object. + The unary plus operator converts its operand to Number type. - The unary negation operator converts its operand to Number type and then negates it. ~ Bitwise NOT operator. ! Logical NOT operator.

Arithmetic operators

Arithmetic operators take numerical values (either literals or variables) as their operands and return a single numerical value.

Relational operators

A comparison operator compares its operands and returns a Boolean value based on whether the comparison is true.

in The in operator determines whether an object has a given property. instanceof The instanceof operator determines whether an object is an instance of another object. < Less than operator. > Greater than operator. <= Less than or equal operator. >= Greater than or equal operator.

Note: => is not an operator, but the notation for Arrow functions.

Equality operators

The result of evaluating an equality operator is always of type Boolean based on whether the comparison is true.

Bitwise shift operators

Operations to shift all bits of the operand.

<< Bitwise left shift operator. >> Bitwise right shift operator. >>> Bitwise unsigned right shift operator.

Binary bitwise operators

Bitwise operators treat their operands as a set of 32 bits (zeros and ones) and return standard JavaScript numerical values.

Binary logical operators

Logical operators are typically used with boolean (logical) values, and when they are, they return a boolean value.

&& Logical AND. || Logical OR. ?? Nullish Coalescing Operator.

Conditional (ternary) operator

(condition ? ifTrue : ifFalse) The conditional operator returns one of two values based on the logical value of the condition.

Optional Chaining operator

?. The optional chaining operator returns undefined instead of causing an error if a reference is nullish ( null or undefined ).

Assignment operators

An assignment operator assigns a value to its left operand based on the value of its right operand.

Comma operator

, The comma operator allows multiple expressions to be evaluated in a single statement and returns the result of the last expression.

Specifications

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

See also