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。
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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
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 | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Array.prototype.keys' in that specification. |
Standard | Initial definition. |
ECMAScript (ECMA-262) The definition of 'Array.prototype.keys' in that specification. |
Living Standard |
瀏覽器相容性
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