Array.prototype.with()

¥Syntax

arrayInstance.with(index, value)

¥Parameters

index

要更改数组的从零开始的索引，转换为整数。

• 负索引从数组末尾开始倒数 — 如果使用 -array.length <= index < 0、index + array.length。
• 如果标准化后的索引越界，则抛出 RangeError。

value

要分配给给定索引的任何值。

¥Return value

一个新数组，其中 index 处的元素替换为 value。

¥A new array with the element at index replaced with value.

¥Exceptions

RangeError

如果是 index >= array.length 或 index < -array.length，则抛出。

¥Description

with() 方法更改数组中给定索引的值，返回一个新数组，其中给定索引处的元素替换为给定值。原始数组没有被修改。这允许你在进行操作时链接数组方法。

¥The with() method changes the value of a given index in the array, returning a new array with the element at the given index replaced with the given value. The original array is not modified. This allows you to chain array methods while doing manipulations.

通过将 with() 与 at() 组合，你可以使用负索引（分别）写入和读取数组。

¥By combining with() with at(), you can both write and read (respectively) an array using negative indices.

with() 方法永远不会产生 稀疏数组。如果源数组稀疏，则空槽将替换为新数组中的 undefined。

¥The with() method never produces a sparse array. If the source array is sparse, the empty slots will be replaced with undefined in the new array.

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

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

¥Examples

¥Creating a new array with a single element changed

const arr = [1, 2, 3, 4, 5];
console.log(arr.with(2, 6)); // [1, 2, 6, 4, 5]
console.log(arr); // [1, 2, 3, 4, 5]

¥Chaining array methods

使用 with() 方法，你可以更新数组中的单个元素，然后应用其他数组方法。

¥With the with() method, you can update a single element in an array and then apply other array methods.

const arr = [1, 2, 3, 4, 5];
console.log(arr.with(2, 6).map((x) => x ** 2)); // [1, 4, 36, 16, 25]

¥Using with() on sparse arrays

with() 方法始终创建密集数组。

¥The with() method always creates a dense array.

const arr = [1, , 3, 4, , 6];
console.log(arr.with(0, 2)); // [2, undefined, 3, 4, undefined, 6]

¥Calling with() on non-array objects

with() 方法创建并返回一个新数组。它读取 this 的 length 属性，然后访问键为小于 length 的非负整数的每个属性。当访问 this 的每个属性时，索引等于该属性键的数组元素将被设置为该属性的值。最后，将 index 处的数组值设置为 value。

¥The with() method creates and returns a new array. It reads the length property of this and then accesses each property whose key is a nonnegative integer less than length. As each property of this is accessed, the array element having an index equal to the key of the property is set to the value of the property. Finally, the array value at index is set to value.

const arrayLike = {
  length: 3,
  unrelated: "foo",
  0: 5,
  2: 4,
  3: 3, // ignored by with() since length is 3
};
console.log(Array.prototype.with.call(arrayLike, 0, 1));
// [ 1, undefined, 4 ]

¥See also

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