左移 (<<)

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.

左移操作符 (<<) 将第一个操作数向左移动指定位数,左边超出的位数将会被清除,右边将会补零。

尝试一下

const a = 5; // 00000000000000000000000000000101
const b = 2; // 00000000000000000000000000000010

console.log(a << b); // 00000000000000000000000000010100
// Expected output: 20

语法

a << b

描述

左移操作符将第一个操作数向左移动指定位数,左边超出的位数将会被清除,右边将会补零。

例如, 9 << 2 得出 36:

js
     9 (十进制): 00000000000000000000000000001001 (二进制)
                 --------------------------------

9 << 2 (十进制): 00000000000000000000000000100100 (二进制) = 36 (十进制)

移动任意数字 x 至左边 y 位,得出 x * 2 ** y。 所以例如:9 << 3 等价于 9 * 2³ = 9 * 8 = 72

示例

使用左移

js
9 << 3; // 72

// 9 * 2³ = 9 * 8 = 72

规范

Specification
ECMAScript® 2025 Language Specification
# sec-left-shift-operator

浏览器兼容性

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
Bitwise left shift (a << b)

Legend

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Full support
Full support

参见