Baseline Widely available
The Array.isArray() static method determines whether the passed value is an Array.
console.log(Array.isArray([1, 3, 5]));
// Expected output: true
console.log(Array.isArray("[]"));
// Expected output: false
console.log(Array.isArray(new Array(5)));
// Expected output: true
console.log(Array.isArray(new Int16Array([15, 33])));
// Expected output: false
value
The value to be checked.
true if value is an Array; otherwise, false. false is always returned if value is a TypedArray instance.
Array.isArray() checks if the passed value is an Array. It performs a branded check, similar to the in operator, for a private field initialized by the Array() constructor.
It is a more robust alternative to instanceof Array because it avoids false positives and false negatives:
Array.isArray() rejects values that aren't actual Array instances, even if they have Array.prototype in their prototype chain â instanceof Array would accept these as it does check the prototype chain.Array.isArray() accepts Array objects constructed in another realm â instanceof Array returns false for these because the identity of the Array constructor is different across realms.See the article "Determining with absolute accuracy whether or not a JavaScript object is an array" for more details.
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 });
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
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4