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.
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
andobject["property"]
). 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. ...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.
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 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.
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.
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
Assignment operators
An assignment operator assigns a value to its left operand based on the value of its right operand.
=
-
Assignment operator.
*=
-
Multiplication assignment.
**=
-
Exponentiation 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.
&&=
-
Logical AND assignment.
||=
-
Logical OR assignment.
??=
-
Logical nullish assignment.
-
[a, b] = [1, 2]
{a, b} = {a:1, b:2}
-
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.
Comma operator
,
-
The comma operator allows multiple expressions to be evaluated in a single statement and returns the result of the last expression.
Specifications
No specification found
No specification data found for javascript.operators
.
Check for problems with this page or contribute a missing spec_url
to mdn/browser-compat-data. Also make sure the specification is included in w3c/browser-specs.
Browser compatibility
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