The logical AND assignment (x &&= y
) operator only assigns if x
is truthy.
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Syntax
expr1 &&= expr2
Description
Short-circuit evaluation
The logical AND operator is evaluated left to right, it is tested for possible short-circuit evaluation using the following rule:
(some falsy expression) && expr
is short-circuit evaluated to the falsy expression;
Short circuit means that the expr
part above is not evaluated, hence any side effects of doing so do not take effect (e.g., if expr
is a function call, the calling never takes place).
Logical AND assignment short-circuits as well meaning that x &&= y
is equivalent to:
x && (x = y);
And not equivalent to the following which would always perform an assignment:
x = x && y;
Examples
Using logical AND assignment
let x = 0; let y = 1; x &&= 0; // 0 x &&= 1; // 0 y &&= 1; // 1 y &&= 0; // 0
Specifications
Specification |
---|
Logical Assignment Operators The definition of 'Assignment operators' in that specification. |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Logical AND assignment (x &&= y ) | Chrome Full support 85 | Edge Full support 85 | Firefox Full support 79 | IE No support No | Opera No support No | Safari Full support 14 | WebView Android Full support 85 | Chrome Android Full support 85 | Firefox Android No support No | Opera Android No support No | Safari iOS Full support 14 | Samsung Internet Android No support No | nodejs No support No |
Legend
- Full support
- Full support
- No support
- No support