Array.of()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.

The Array.of() static method creates a new Array instance from a variable number of arguments, regardless of number or type of the arguments.

Try it

console.log(Array.of("foo", 2, "bar", true));
// Expected output: Array ["foo", 2, "bar", true]

console.log(Array.of());
// Expected output: Array []

Syntax

js
Array.of()
Array.of(element1)
Array.of(element1, element2)
Array.of(element1, element2, /* …, */ elementN)

Parameters

element1, …, elementN

Elements used to create the array.

The difference between Array.of() and the Array() constructor is in the handling of single arguments: Array.of(7) creates an array with a single element, 7, whereas Array(7) creates an empty array with a length property of 7. (That implies an array of 7 empty slots, not slots with actual undefined values.)

js
Array.of(7); // [7]
Array(7); // array of 7 empty slots

Array.of(1, 2, 3); // [1, 2, 3]
Array(1, 2, 3); // [1, 2, 3]

The Array.of() method is a generic factory method. For example, if a subclass of Array inherits the of() method, the inherited of() method will return new instances of the subclass instead of Array instances. In fact, the this value can be any constructor function that accepts a single argument representing the length of the new array, and the constructor will be called with the number of arguments passed to of(). The final length will be set again when all elements are assigned. If the this value is not a constructor function, the plain Array constructor is used instead.

Examples

Using Array.of()

js
Array.of(1); // [1]
Array.of(1, 2, 3); // [1, 2, 3]
Array.of(undefined); // [undefined]

Calling of() on non-array constructors

The of() method can be called on any constructor function that accepts a single argument representing the length of the new array.

js
function NotArray(len) {
  console.log("NotArray called with length", len);
}

console.log(Array.of.call(NotArray, 1, 2, 3));
// NotArray called with length 3
// NotArray { '0': 1, '1': 2, '2': 3, length: 3 }

console.log(Array.of.call(Object)); // [Number: 0] { length: 0 }

When the this value is not a constructor, a plain Array object is returned.

console.log(Array.of.call({}, 1)); // [ 1 ]