Widely available Supported across all major browsers. Safe to use in production.

Logical assignments

The logical AND assignment (&&=) operator only evaluates the right operand and assigns to the left if the left operand is truthy.

Language core

Browser support

Feature Desktop Mobile
Chrome
Edge
Firefox
Safari
Chrome Android
Safari iOS
logical_and_assignment
85
85
79
14
85
14
Other
javascript.operators.logical_or_assignment

The logical OR assignment (||=) operator only evaluates the right operand and assigns to the left if the left operand is falsy.
85
85
79
14
85
14
1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)

Syntax

JAVASCRIPT 
let a = null;
a ??= 'default'; // a is 'default'

let b = '';
b ||= 'fallback'; // b is 'fallback'

let c = 'hello';
c &&= c.toUpperCase(); // c is 'HELLO'

Live demo

Orassignment (||=)

variable that falsevalue(emptycharacter, 0 etc). And onlyassignment..

PreviewFullscreen

Andassignment (&&=)

variable that truevalue. And onlyassignment..

PreviewFullscreen

Nullcombinebodyassignment (??=)

variable that null is undefined. And onlyassignment..

PreviewFullscreen

Use cases

  • Using Logical assignments

    The logical AND assignment (&&=) operator only evaluates the right operand and assigns to the left if the left operand is truthy.

Cautions

  • No specific concerns. Stable across all major browsers.

Accessibility

  • When updating the DOM dynamically, announce important changes to assistive technology with aria-live regions.

Related links