Exponentiation assignment (**=)
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2017.
The exponentiation assignment (**=) operator performs exponentiation on the two operands and assigns the result to the left operand.
Try it
let a = 3;
console.log((a **= 2));
// Expected output: 9
console.log((a **= 0));
// Expected output: 1
console.log((a **= 'hello'));
// Expected output: NaN
Syntax
js
x **= y
Description
x **= y is equivalent to x = x ** y, except that the expression x is only evaluated once.
Examples
Exponentiation assignment using numbers
js
let bar = 5;
bar **= 2; // 25
Other non-BigInt values are coerced to numbers:
js
let baz = 5;
baz **= "foo"; // NaN
Exponentiation assignment using BigInts
js
let foo = 3n;
foo **= 2n; // 9n
foo **= 1; // TypeError: Cannot mix BigInt and other types, use explicit conversions
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-assignment-operators |