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 runt

Answer 1

Object.keys(Array.apply(0, Array(3))).map(Number)

Returns [0, 1, 2]. Very similar to Igor Shubin's excellent answer, but with slightly less trickery (and one character longer).

Explanation:

• Array(3) // [undefined × 3] Generate an array of length n=3. Unfortunately this array is almost useless to us, so we have to…
• Array.apply(0,Array(3)) // [undefined, undefined, undefined] make the array iterable. Note: null's more common as apply's first arg but 0's shorter.
• Object.keys(Array.apply(0,Array(3))) // ['0', '1', '2'] then get the keys of the array (works because Arrays are the typeof array is an object with indexes for keys.
• Object.keys(Array.apply(0,Array(3))).map(Number) // [0, 1, 2] and map over the keys, converting strings to numbers.