How to initialize an array of the first ten integers briefly?

Question

I'm studying Ruby and JavaScript. Occasionally I want an array of the first ten integers (or some other predictable series):

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

In Ruby, is there a faster (like, built in) way to initialize this array than (0..9).to_a? Anyway, that's pretty fast.

But in JavaScript, I don't know of any similarly fast way to build it. I could iterate over a for loop but I figure there has to be a faster way. But what is it?

What is your definition of _faster_? _Faster_ to type (aka shorter), _faster_ to read (easy to understand) or the code runs _faster_ (low memory consumption, fewer cycles - benchmarked)? — spickermann, Nov 13 '17 at 06:21
Changed "How to initialize an array of the first ten integers faster than this?" to "How to initialize an array of the first ten integers briefly?" — globewalldesk, Nov 13 '17 at 19:32

score 6 · Accepted Answer · answered Nov 12 '17 at 22:22

6

You can use spread syntax in combination with keys() method.

console.log([ ...Array(10).keys() ]);

Another way is to use Array.from method.

console.log(Array.from({length: 10}, (_, k) => k));

answered Nov 12 '17 at 22:22

Mihai Alexandru-Ionut

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I was thinking it would involve the spread operator, I just didn't see how. Now I know! – globewalldesk Nov 13 '17 at 01:21

How to initialize an array of the first ten integers briefly?

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