Array.isArray()

¥Syntax

Array.isArray(value)

¥Parameters

value

要检查的值。

¥Return value

如果 value 是 Array，则 true；否则，false。如果 value 是 TypedArray 实例，则始终返回 false。

¥true if value is an Array; otherwise, false. false is always returned if value is a TypedArray instance.

¥Description

Array.isArray() 检查传递的值是否为 Array。它不检查值的原型链，也不依赖于它所附加的 Array 构造函数。对于使用数组文字语法或 Array 构造函数创建的任何值，它都会返回 true。这使得跨字段对象的使用变得安全，其中 Array 构造函数的标识不同，因此会导致 instanceof Array 失败。

¥Array.isArray() checks if the passed value is an Array. It does not check the value's prototype chain, nor does it rely on the Array constructor it is attached to. It returns true for any value that was created using the array literal syntax or the Array constructor. This makes it safe to use with cross-realm objects, where the identity of the Array constructor is different and would therefore cause instanceof Array to fail.

有关更多详细信息，请参阅文章 "绝对准确地确定 JavaScript 对象是否是数组"。

¥See the article "Determining with absolute accuracy whether or not a JavaScript object is an array" for more details.

Array.isArray() 还拒绝其原型链中带有 Array.prototype 的对象，但它们不是实际的数组，而 instanceof Array 会接受。

¥Array.isArray() also rejects objects with Array.prototype in its prototype chain but aren't actual arrays, which instanceof Array would accept.

¥Examples

¥Using Array.isArray()

// all following calls return true
Array.isArray([]);
Array.isArray([1]);
Array.isArray(new Array());
Array.isArray(new Array("a", "b", "c", "d"));
Array.isArray(new Array(3));
// Little known fact: Array.prototype itself is an array:
Array.isArray(Array.prototype);

// all following calls return false
Array.isArray();
Array.isArray({});
Array.isArray(null);
Array.isArray(undefined);
Array.isArray(17);
Array.isArray("Array");
Array.isArray(true);
Array.isArray(false);
Array.isArray(new Uint8Array(32));
// This is not an array, because it was not created using the
// array literal syntax or the Array constructor
Array.isArray({ __proto__: Array.prototype });

¥instanceof vs. Array.isArray()

检查 Array 实例时，Array.isArray() 优于 instanceof，因为它可以跨字段工作。

¥When checking for Array instance, Array.isArray() is preferred over instanceof because it works across realms.

const iframe = document.createElement("iframe");
document.body.appendChild(iframe);
const xArray = window.frames[window.frames.length - 1].Array;
const arr = new xArray(1, 2, 3); // [1, 2, 3]

// Correctly checking for Array
Array.isArray(arr); // true
// The prototype of arr is xArray.prototype, which is a
// different object from Array.prototype
arr instanceof Array; // false

¥See also

• core-js 中 Array.isArray 的 Polyfill
• 索引集合 指南
• Array