Array.prototype.keys()
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.
keys() 方法會回傳一個包含陣列中的每一個索引之鍵（keys）的新 Array Iterator 物件。
嘗試一下
const array1 = ["a", "b", "c"];
const iterator = array1.keys();
for (const key of iterator) {
console.log(key);
}
// Expected output: 0
// Expected output: 1
// Expected output: 2
語法
arr.keys()
回傳值
一個新的 Array 迭代器（iterator）物件。
範例
鍵迭代器不會乎略陣列中的空元素
js
var arr = ["a", , "c"];
var sparseKeys = Object.keys(arr);
var denseKeys = [...arr.keys()];
console.log(sparseKeys); // ['0', '2']
console.log(denseKeys); // [0, 1, 2]
規範
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-array.prototype.keys |
瀏覽器相容性
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