Array.from

The Array.from() static method creates a new, shallow-copied Array instance from an iterable or array-like object.

Syntax

Array.from(arrayLike)

// Arrow function
Array.from(arrayLike, (element) => { /* … */ })
Array.from(arrayLike, (element, index) => { /* … */ })

// Mapping function
Array.from(arrayLike, mapFn)
Array.from(arrayLike, mapFn, thisArg)

// Inline mapping function
Array.from(arrayLike, function (element) { /* … */ })
Array.from(arrayLike, function (element, index) { /* … */ })
Array.from(arrayLike, function (element) { /* … */ }, thisArg)
Array.from(arrayLike, function (element, index) { /* … */ }, thisArg)

Parameters

• arrayLike

  • : An iterable or array-like object to convert to an array.

• mapFn optional

  • : Map function to call on every element of the array. If provided, every value to be added to the array is first passed through this function, and mapFn's return value is added to the array instead.

    The function is called with the following arguments:

    • element
      • : The current element being processed in the array.
    • index
      • : The index of the current element being processed in the array.

• thisArg optional

  • : Value to use as this when executing mapFn.

Return value

A new Array instance.

Description

Array.from() lets you create Arrays from:

• iterable objects (objects such as Map and Set; or, if the object is not iterable,
• array-like objects (objects with a length property and indexed elements).

Array.from() never creates a sparse array. If the arrayLike object is missing some index properties, they become undefined in the new array.

Array.from() has an optional parameter mapFn, which allows you to execute a function on each element of the array being created, similar to Array.prototype.map(). More clearly, Array.from(obj, mapFn, thisArg) has the same result as Array.from(obj).map(mapFn, thisArg), except that it does not create an intermediate array, and mapFn only receives two arguments (element, index) without the whole array, because the array is still under construction.