Left shift assignment (<<=)
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Theleft shift assignment (<<=) operator performsleft shift on the two operands and assigns the result to the left operand.
Try it
let a = 5; // 00000000000000000000000000000101a <<= 2; // 00000000000000000000000000010100console.log(a);// Expected output: 20Syntax
js
x <<= yDescription
x <<= y is equivalent tox = x << y, except that the expressionx is only evaluated once.
Examples
Using left shift assignment
js
let a = 5;// 00000000000000000000000000000101a <<= 2; // 20// 00000000000000000000000000010100let b = 5n;b <<= 2n; // 20nSpecifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-assignment-operators |