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Addition

The addition operator (+) produces the sum of numeric operands or string concatenation.

Syntax

Operator: x + y

Examples

Numeric addition

// Number + Number -> addition
1 + 2 // 3

// Boolean + Number -> addition
true + 1 // 2

// Boolean + Boolean -> addition
false + false // 0

String concatenation

// String + String -> concatenation
'foo' + 'bar' // "foobar"

// Number + String -> concatenation
5 + 'foo' // "5foo"

// String + Boolean -> concatenation
'foo' + false // "foofalse"

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Addition (+) 1 12 1 3 3 1
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
Addition (+) 1 18 4 10.1 1 1.0
Server
Node.js
Addition (+) 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/Addition