arithmetic sequence: use apply or map instead of for loop

Question

I have a for loop like so:

var myary = [];
for(i=0; i<3; i++){
  myary[i] = i;
}
//yields [0, 1, 2]

I'd like to accomplish the same with myary.apply() or a functional equivalent, but I am not familiar with generating arithmetic sequences via functional methods in JavaScript. Is this possible?

Check out [Creating range in JS](http://stackoverflow.com/q/18947892/1048572) — Bergi, May 06 '15 at 20:03
possible duplicate of [Functional approach to basic array construction](http://stackoverflow.com/a/11808876/1048572) — Bergi, May 06 '15 at 20:06
@Bergi Any reason you didn't close the question as duplicate ? — Denys Séguret, May 06 '15 at 20:09
@dystroy: Because it's not an exact duplicate. If you think that's fine, throw your hammer; I wanted to wait for confirmation by jml whether it answered his question. — Bergi, May 06 '15 at 20:12
@Bergi Hum... right, not exactly a duplicate. I'll let OP (or somebody else decide) — Denys Séguret, May 06 '15 at 20:13
@Bergi - agreed. IMO, this is more about generating sequences w/ said approaches, rather than a more general query. — jml, May 06 '15 at 20:34

Denys Séguret · Accepted Answer · 2015-05-11T13:00:34.613

1

There's no clean and easy functional solution in ES5. Here's the simplest I have:

var myary = Array.apply(0,Array(N)).map(function(_,i){return i});

Edit: Be careful that expressions of this kind, while being sometimes convenient, can be very slow. This commit I made was motivated by performance issues. An old style and boring for loop can often be much faster.

edited May 11 '15 at 13:00

answered May 06 '15 at 20:00

Denys Séguret

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although maybe not "clean" or "easy", I find this to be readable. – jml May 06 '15 at 20:08
`Function.call.bind(Number)` is a good way to get arguments[1] without a custom... – dandavis May 06 '15 at 21:42
1

@jml Just in case, you might want to check my edit, so that you don't painfully discover later the reason of a slowdown in your application. – Denys Séguret May 11 '15 at 13:01

arithmetic sequence: use apply or map instead of for loop

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