How to create an array containing 1...N

Question

I'm looking for any alternatives to the below for creating a JavaScript array containing 1 through to N where N is only known at runtime.

var foo = [];  for (var i = 1; i <= N; i++) {    foo.push(i); } 

To me it feels like there should be a way of doing this without the loop.

Answer 1

In ES6 using Array from() and keys() methods.

Array.from(Array(10).keys()) //=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 

Shorter version using spread operator.

[...Array(10).keys()] //=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 

Start from 1 by passing map function to Array from(), with an object with a length property:

Array.from({length: 10}, (_, i) => i + 1) //=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]