Javascript Array.from()

// creating a new array from string
let newArray = Array.from("abc");

console.log(newArray);

// Output:
// [ 'a', 'b', 'c' ]

from() Syntax

The syntax of the from() method is:

Array.from(arraylike, mapFunc, thisArg)

The from() method, being a static method, is called using the Array class name.

from() Parameters

The from() method can take three parameters:

• arraylike - Array-like or iterable object to convert to an array.
• mapFunc (optional) - Map function that is called on each element.
• thisArg (optional) - Value to use as this when executing mapFunc.

Note: Array.from(obj, mapFunc, thisArg) is equivalent to Array.from(obj).map(mapFunc, thisArg).

from() Return Value

• Returns a new Array instance.

Example 1: from() Method with Array-like Objects

// creating an array from a string 
let array1= Array.from("JavaScript");

console.log(array1); 

Output

['J', 'a', 'v', 'a', 'S', 'c', 'r', 'i', 'p', 't']

In the above example, we have used the from() method to create a new array from the 'JavaScript' string.

We have called the method using Array class as Array.from("JavaScript"). The method returns a new array ['J', 'a', 'v', 'a', 'S', 'c', 'r', 'i', 'p', 't'] and assigns it to array1.

Example 2: from() Method with Mapping Function

// function that returns a new array
function createArray(arraylike, mapFunc) {
  return Array.from(arraylike, mapFunc);
}

// using arrow function for mapFunc
let result = createArray([2, 4, 6], (element) => element + 2);

console.log(result);

Output

[ 4, 6, 8 ]

In the above example, we have passed a mapping function in the from() method that increases every element of the array being created by 2.

Example 2: from() Method with a Set

// defining a Set
let set = new Set(["JavaScript", "Python", "Go", "Python"]);

// creating an array from the given  set
let result = Array.from(set);

console.log(result);

Output

[ 'JavaScript', 'Python', 'Go' ]

Here, we have created a new array using the from() method with an iteratable object- Set.

Recommended Reading: JavaScript Array map()