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

There is another way in ES6, using Array.from which takes 2 arguments, the first is an arrayLike (in this case an object with length property), and the second is a mapping function (in this case we map the item to its index)

Array.from({length:10}, (v,i) => i)

this is shorter and can be used for other sequences like generating even numbers

Array.from({length:10}, (v,i) => i*2)

Also this has better performance than most other ways because it only loops once through the array. Check the snippit for some comparisons

// open the dev console to see results

count = 100000

console.time("from object")
for (let i = 0; i i )
}
console.timeEnd("from object")

console.time("from keys")
for (let i =0; i