遞增運算子（++）
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
遞增運算子（++）遞增（加一）它的運算元並將結果回傳。
嘗試一下
let x = 3; const y = x++; console.log(`x:${x}, y:${y}`); // Expected output: "x:4, y:3" let a = 3; const b = ++a; console.log(`a:${a}, b:${b}`); // Expected output: "a:4, b:4" 語法
js
x++ ++x 詳細說明
若將遞增運算子作為後綴（例如 x++），則會先回傳原本的值，再進行遞增。
若作為前綴（例如 ++x），則會先進行遞增，再將遞增後的結果回傳。
範例
遞增運算子置於後綴
js
let x = 3; y = x++; // y = 3 // x = 4 遞增運算子置於前綴
js
let a = 2; b = ++a; // a = 3 // b = 3 規範
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-postfix-increment-operator |
