The addition assignment operator (+=
) adds the value of the right operand to a variable and assigns the result to the variable. The types of the two operands determine the behavior of the addition assignment operator. Addition or concatenation is possible.
Addition assignment (+=)
Try it
Syntax
x += y // x = x + y
Examples
Using addition assignment
// Assuming the following variables // foo = 'foo' // bar = 5 // baz = true // Number + Number -> addition bar += 2 // 7 // Boolean + Number -> addition baz += 1 // 2 // Boolean + Boolean -> addition baz += false // 1 // Number + String -> concatenation bar += 'foo' // "5foo" // String + Boolean -> concatenation foo += false // "foofalse" // String + String -> concatenation foo += 'bar' // "foobar"
Specifications
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
Addition_assignment |
1
|
12
|
1
|
3
|
3
|
1
|
1
|
18
|
4
|
10.1
|
1
|
1.0
|
1.0
|
0.10.0
|
See also
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Addition_assignment