べき乗代入 (**=)

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.

べき乗代入演算子 (**=) は、変数の値を右オペランドでべき乗します。

試してみましょう

let a = 3;

console.log((a **= 2));
// Expected output: 9

console.log((a **= 0));
// Expected output: 1

console.log((a **= "hello"));
// Expected output: NaN

構文

js
x **= y; // x = x ** y

べき乗代入の仕様

js
// 次の変数を想定
//  bar = 5

bar **= 2; // 25
bar **= "foo"; // NaN

仕様書

Specification
ECMAScript® 2025 Language Specification
# sec-assignment-operators

ブラウザーの互換性

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
Exponentiation assignment (x **= y)

Legend

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Full support
Full support

関連情報