一元負號運算子（-）

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since 2015年7月.

一元負號運算子（-）置於運算元之前，並將運算元轉為其負值。

嘗試一下

const x = 4;
const y = -x;

console.log(y);
// Expected output: -4

const a = "4";
const b = -a;

console.log(b);
// Expected output: -4

-x

js
const x = 3;
const y = -x;

// y = -3
// x = 3

一元負號運算子可以將非數字轉為數字。

js
const x = "4";
const y = -x;

// y = -4

Specification

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This page was last modified on 2025年7月16日 by MDN contributors.