Expressions and operators
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. These expressions have the highest precedence (higher than operators).
this
-
The
this
keyword refers to a special property of an execution context. - Literals
-
Basic
null
, boolean, number, and string literals. []
-
Array initializer/literal syntax.
{}
-
Object initializer/literal syntax.
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. async function
-
The
async function
defines an async function expression. async function*
-
The
async function*
keywords define an async generator function expression. /ab+c/i
-
Regular expression literal syntax.
`string`
-
Template 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
andobject["property"]
). ?.
-
The optional chaining operator returns
undefined
instead of causing an error if a reference is nullish (null
orundefined
). new
-
The
new
operator creates an instance of a constructor. new.target
-
In constructors,
new.target
refers to the constructor that was invoked bynew
. import.meta
-
An object exposing context-specific metadata to a JavaScript module.
super
-
The
super
keyword calls the parent constructor or allows accessing properties of the parent object. import()
-
The
import()
syntax allows loading a module asynchronously and dynamically into a potentially non-module environment.
Increment and decrement
Unary operators
A unary operation is an operation with only one operand.
delete
-
The
delete
operator deletes a property from an object. void
-
The
void
operator evaluates an expression and discards its 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.
await
-
Pause and resume an async function and wait for the promise's fulfillment/rejection.
Arithmetic operators
Relational operators
A comparison operator compares its operands and returns a boolean value based on whether the comparison is true.
<
(Less than)-
Less than operator.
>
(Greater than)-
Greater than operator.
<=
-
Less than or equal operator.
>=
-
Greater than or equal operator.
instanceof
-
The
instanceof
operator determines whether an object is an instance of another object. in
-
The
in
operator determines whether an object has a given property.
Note: =>
is not an operator, but the notation for Arrow functions.
Equality operators
Bitwise shift operators
Binary bitwise operators
Binary logical operators
Logical operators implement boolean (logical) values and have short-circuiting behavior.
Conditional (ternary) operator
(condition ? ifTrue : ifFalse)
-
The conditional operator returns one of two values based on the logical value of the condition.
Assignment operators
An assignment operator assigns a value to its left operand based on the value of its right operand.
=
-
Assignment operator.
*=
-
Multiplication assignment.
/=
-
Division assignment.
%=
-
Remainder assignment.
+=
-
Addition assignment.
-=
-
Subtraction assignment
<<=
-
Left shift assignment.
>>=
-
Right shift assignment.
>>>=
-
Unsigned right shift assignment.
&=
-
Bitwise AND assignment.
^=
-
Bitwise XOR assignment.
|=
-
Bitwise OR assignment.
**=
-
Exponentiation assignment.
&&=
-
Logical AND assignment.
||=
-
Logical OR assignment.
??=
-
Nullish coalescing assignment.
[a, b] = arr
,{ a, b } = obj
-
Destructuring assignment allows you to assign the properties of an array or object to variables using syntax that looks similar to array or object literals.
Yield operators
Spread syntax
...obj
-
Spread syntax allows an iterable, such as an array or string, to be expanded in places where zero or more arguments (for function calls) or elements (for array literals) are expected. In an object literal, the spread syntax enumerates the properties of an object and adds the key-value pairs to the object being created.
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
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