May 15, 2017

Array From 0 to N

Posted In: "development"

This short post intended to show how easy it is to create an array with 0 - n with ES6 version of JavaScript. Old way:

var arr = [];
for(var i = 0; i <= 10; i++) {
	arr.push(i);
}

arr // [0,1,2,3,4,5,6,7,8,9,10];

New ES6 way:

let arr = [...Array(11).keys()];

arr // [0,1,2,3,4,5,6,7,8,9,10];

What exactly is happening here?

First with Array(n) we are creating an empty array with N length, the value of each item in the list is undefined.

However, when we get the keys of an array using .keys() method, we are getting list of indexes.

Lastly, since .keys() method returns an “Array Iterator”, we are spreading out this result into a new array using the spread operator.