In Javascript, what is the most compact, elegant and efficent way to bring the last element of an array to the beginning?

Question

I'm programming a Snake game

and the logic of the snake's movement dictates that if I have a Javascript array

var links = [elem_0, elem_1, ..., elem_n];

of elements representing links of the snake, then the way for the snake to move is to pop out elem_n, change its position to be that of the elem_0 plus the translation units dx and dy, and then put it at the beginning of the array:

[elem_0, elem_1, ..., elem_n] ---> [elem_n, elem_0, ..., elem_(n-1)]

(with some internal properties of elem_n changed in the process)

What is the way to do this that makes no compromise between

optimally efficient in number of operations and memory usage
readable
maintainable
clever (optional)
elegant
compact

????

Clever is never a requirement of mine. "Optimally efficient" is an ill-defined target. What is generally needed is the least amount of effort to achieve a solution that meets the requirements. This leaves more time to work on other areas of the problem that matter. Since you've not defined what would be sufficient, we can't code to a particular goal. Plus, maximum efficiency often requires adding complication which conflicts with many of your other goals so one must know how to make a tradeoff between them. — jfriend00, Jul 28 '15 at 06:18
possible duplicate of [JavaScript Array rotate()](http://stackoverflow.com/questions/1985260/javascript-array-rotate) — , Jul 28 '15 at 06:41

spender · Accepted Answer · 2015-07-28T06:13:37.900

optimally efficient in number of operations and memory usage

You're asking for two optimisations that usually counter one another. e.g. more speed == more memory.

That said, I'd probably choose a (doubly) linked list to store my snake, because removal or addition at the front or tail are very cheap, and with games, faster is way preferable to less memory (within reason, but I wonder how long your snake would have to be before you run into memory issues... well beyond what's playable... and some).

Of course, I assume you've measured and found the standard array based methods to be too slow (seems unlikely).

VamsiKaja · Answer 2 · 2015-07-28T06:29:08.000

3

You can rotate an array in two ways :

links.unshift(links.pop());   or

links.push(links.shift());

first method solves your issue.

edited Jul 28 '15 at 06:29

answered Jul 28 '15 at 06:15

VamsiKaja

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score 2 · Answer 3 · edited Jul 28 '15 at 06:13

2

For any version of Javascript from ES3 forward:

links.unshift(links.pop());

edited Jul 28 '15 at 06:13

jfriend00

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answered Jul 28 '15 at 06:07

Vidul

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I mean the future versions: 6 and 7. – Vidul Jul 28 '15 at 06:10
Seems like the simplest solution until some justification for something more complex is provided. Is also readable, maintainable, compact and simple. – jfriend00 Jul 28 '15 at 06:13

In Javascript, what is the most compact, elegant and efficent way to bring the last element of an array to the beginning?

3 Answers3