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.
The left shift assignment (<<=) operator performs left shift on the two operands and assigns the result to the left operand.
Try it
let a = 5; // 00000000000000000000000000000101
a <<= 2; // 00000000000000000000000000010100
console.log(a);
// Expected output: 20
Syntax
js
x <<= y
Description
x <<= y is equivalent to x = x << y, except that the expression x is only evaluated once.
Examples
Using left shift assignment
js
let a = 5;
// 00000000000000000000000000000101
a <<= 2; // 20
// 00000000000000000000000000010100
let b = 5n;
b <<= 2n; // 20n
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-assignment-operators |