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 May 2018.
Метод keys()
возвращает новый итератор массива Array Iterator
, содержащий ключи каждого индекса в массиве.
Интерактивный пример
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
Синтаксис
arr.keys()
Примеры
Пример: базовое использование
js
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 }
Пример: итератор, возвращаемый методом keys()
, не пропускает дырки в массиве
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]
Спецификации
Specification |
---|
ECMAScript® 2025 Language Specification # sec-array.prototype.keys |
Совместимость с браузерами
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keys |
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- Full support
- Full support
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