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Decrement

The decrement operator (--) decrements (subtracts one from) its operand and returns a value.

Syntax

Operator: x-- or --x

Description

If used postfix, with operator after operand (for example, x--), the decrement operator decrements and returns the value before decrementing.

If used prefix, with operator before operand (for example, --x), the decrement operator decrements and returns the value after decrementing.

Examples

Postfix decrement

let x = 3;
y = x--;

// y = 3
// x = 2

Prefix decrement

let a = 2;
b = --a;

// a = 1
// b = 1

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Decrement (--) 2 12 1 3 3 4
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
Decrement (--) 1 18 4 10.1 3.2 1.0
Server
Node.js
Decrement (--) 0.1.100

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Decrement