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This feature is well established and works across many devices and browser versions. Its been available across browsers since 2015 ..
keys() Array Iterator, .
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
arr.keys()
var arr = ["a", "b", "c"];
var iterator = arr.keys();
console.log(iterator.next()); // { value: 0, done: false }
console.log(iterator.next()); // { value: 1, done: false }
console.log(iterator.next()); // { value: 2, done: false }
console.log(iterator.next()); // { value: undefined, done: true }
keys(), var arr = ["a", , "c"];
var sparseKeys = Object.keys(arr);
var denseKeys = [...arr.keys()];
console.log(sparseKeys); // [0, 2]
console.log(denseKeys); // [0, 1, 2]
| Specification |
|---|
| ECMAScript 2027 LanguageSpecification # sec-array.prototype.keys |
This page was last modified on 17 . 2025 . by MDN contributors.
ArrayArray.prototype.at()Array.prototype.concat()Array.prototype.copyWithin()Array.prototype.entries()Array.prototype.every()Array.prototype.fill()Array.prototype.filter()Array.prototype.find()Array.prototype.findIndex()findLast()findLastIndex()Array.prototype.flat()Array.prototype.flatMap()Array.prototype.forEach()Array.prototype.includes()Array.prototype.indexOf()Array.prototype.join()Array.prototype.keys()Array.prototype.lastIndexOf()Array.prototype.map()Array.prototype.pop()Array.prototype.push()Array.prototype.reduce()Array.prototype.reduceRight()Array.prototype.reverse()Array.prototype.shift()Array.prototype.slice()Array.prototype.some()Array.prototype.sort()Array.prototype.splice()Array.prototype.toLocaleString()Array.prototype.toReversed()Array.prototype.toSorted()toSpliced()Array.prototype.toString()Array.prototype.unshift()Array.prototype.values()Array.prototype.with()Array.prototype[@@iterator]()Object/FunctionObject.prototype.__defineGetter__()Object.prototype.__defineSetter__()Object.prototype.__lookupGetter__()Object.prototype.__lookupSetter__()Object.prototype.hasOwnProperty()Object.prototype.isPrototypeOf()Object.prototype.propertyIsEnumerable()Object.prototype.toLocaleString()Object.prototype.toString()Object.prototype.valueOf()Your blueprint for a better internet.
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