类型错误：无法删除不可配置的数组元素

¥Message

TypeError: Cannot delete property '1' of [object Array] (V8-based)
TypeError: can't delete non-configurable array element (Firefox)
TypeError: Unable to delete property. (Safari)

¥Error type

¥What went wrong?

尝试对数组进行 缩短长度，但数组的元素之一是 non-configurable。当缩短数组时，超出新数组长度的元素将被删除，这种情况会失败。

¥It was attempted to shorten the length of an array, but one of the array's elements is non-configurable. When shortening an array, the elements beyond the new array length will be deleted, which failed in this situation.

configurable 属性控制是否可以从对象中删除该属性以及是否可以更改其属性（writable 除外）。

¥The configurable attribute controls whether the property can be deleted from the object and whether its attributes (other than writable) can be changed.

通常，数组初始值设定项 创建的对象中的属性是可配置的。但是，例如，当使用 Object.defineProperty() 时，默认情况下该属性不可配置。

¥Usually, properties in an object created by an array initializer are configurable. However, for example, when using Object.defineProperty(), the property isn't configurable by default.

¥Examples

¥Non-configurable properties created by Object.defineProperty

如果你未将它们指定为可配置，则 Object.defineProperty() 默认情况下会创建不可配置的属性。

¥The Object.defineProperty() creates non-configurable properties by default if you haven't specified them as configurable.

"use strict";
const arr = [];
Object.defineProperty(arr, 0, { value: 0 });
Object.defineProperty(arr, 1, { value: "1" });

arr.length = 1;
// TypeError: can't delete non-configurable array element

如果你打算缩短数组，则需要将元素设置为可配置。

¥You will need to set the elements as configurable, if you intend to shorten the array.

"use strict";
const arr = [];
Object.defineProperty(arr, 0, { value: 0, configurable: true });
Object.defineProperty(arr, 1, { value: "1", configurable: true });

arr.length = 1;

¥Sealed Arrays

Object.seal() 函数将所有现有元素标记为不可配置。

¥The Object.seal() function marks all existing elements as non-configurable.

"use strict";
const arr = [1, 2, 3];
Object.seal(arr);

arr.length = 1;
// TypeError: can't delete non-configurable array element

你需要删除 Object.seal() 调用，或者复制它。对于副本，缩短数组的副本不会修改原始数组的长度。

¥You either need to remove the Object.seal() call, or make a copy of it. In case of a copy, shortening the copy of the array does not modify the original array length.

"use strict";
const arr = [1, 2, 3];
Object.seal(arr);

// Copy the initial array to shorten the copy
const copy = Array.from(arr);
copy.length = 1;
// arr.length === 3

¥See also

• [[可配置]]
• length
• Object.defineProperty()
• Object.seal()