Array.prototype.toReversed()

¥Syntax

toReversed()

¥Parameters

没有任何。

¥None.

¥Return value

包含相反顺序元素的新数组。

¥A new array containing the elements in reversed order.

¥Description

toReversed() 方法以相反的顺序转置调用数组对象的元素并返回一个新数组。

¥The toReversed() method transposes the elements of the calling array object in reverse order and returns a new array.

当在 稀疏数组 上使用时，toReversed() 方法会迭代空槽，就好像它们具有值 undefined 一样。

¥When used on sparse arrays, the toReversed() method iterates empty slots as if they have the value undefined.

toReversed() 方法是 generic。它只期望 this 值具有 length 属性和整数键控属性。

¥The toReversed() method is generic. It only expects the this value to have a length property and integer-keyed properties.

¥Examples

¥Reversing the elements in an array

以下示例创建一个包含三个元素的数组 items，然后创建一个与 items 相反的新数组。items 数组保持不变。

¥The following example creates an array items, containing three elements, then creates a new array that's the reverse of items. The items array remains unchanged.

const items = [1, 2, 3];
console.log(items); // [1, 2, 3]

const reversedItems = items.toReversed();
console.log(reversedItems); // [3, 2, 1]
console.log(items); // [1, 2, 3]

¥Using toReversed() on sparse arrays

toReversed() 的返回值永远不会稀疏。返回数组中的空槽变为 undefined。

¥The return value of toReversed() is never sparse. Empty slots become undefined in the returned array.

console.log([1, , 3].toReversed()); // [3, undefined, 1]
console.log([1, , 3, 4].toReversed()); // [4, 3, undefined, 1]

¥Calling toReversed() on non-array objects

toReversed() 方法读取 this 的 length 属性。然后，它按降序访问具有 length - 1 和 0 之间整数键的每个属性，将当前属性的值添加到要返回的数组的末尾。

¥The toReversed() method reads the length property of this. It then visits each property having an integer key between length - 1 and 0 in descending order, adding the value of the current property to the end of the array to be returned.

const arrayLike = {
  length: 3,
  unrelated: "foo",
  2: 4,
};
console.log(Array.prototype.toReversed.call(arrayLike));
// [4, undefined, undefined]
// The '0' and '1' indices are not present so they become undefined

¥See also

• core-js 中 Array.prototype.toReversed 的 Polyfill
• 索引集合 指南
• Array.prototype.reverse()
• Array.prototype.toSorted()
• Array.prototype.toSpliced()
• Array.prototype.with()
• TypedArray.prototype.toReversed()