Increment (++)

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The increment (++) operator increments (adds one to) its operand and returns the value before or after the increment, depending on where the operator is placed.

Try it

let x = 3;
const y = x++;

console.log(`x:${x}, y:${y}`);
// Expected output: "x:4, y:3"

let a = 3;
const b = ++a;

console.log(`a:${a}, b:${b}`);
// Expected output: "a:4, b:4"

Syntax

js
x++
++x

Description

The ++ operator is overloaded for two types of operands: number and BigInt. It first coerces the operand to a numeric value and tests the type of it. It performs BigInt increment if the operand becomes a BigInt; otherwise, it performs number increment.

If used postfix, with operator after operand (for example, x++), the increment operator increments and returns the value before incrementing.

If used prefix, with operator before operand (for example, ++x), the increment operator increments and returns the value after incrementing.

The increment operator can only be applied on operands that are references (variables and object properties; i.e. valid assignment targets). ++x itself evaluates to a value, not a reference, so you cannot chain multiple increment operators together.

js
++(++x); // SyntaxError: Invalid left-hand side expression in prefix operation

Examples

Postfix increment

js
let x = 3;
const y = x++;
// x is 4; y is 3

let x2 = 3n;
const y2 = x2++;
// x2 is 4n; y2 is 3n

Prefix increment

js
let x = 3;
const y = ++x;
// x is 4; y is 4

let x2 = 3n;
const y2 = ++x2;
// x2 is 4n; y2 is 4n

Specifications

Specification
ECMAScript® 2025 Language Specification
# sec-postfix-increment-operator

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
Increment (++)

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support

See also