Rotate the elements in an array in JavaScript

You can use push(), pop(), shift() and unshift() methods:

function arrayRotate(arr, reverse) {  if (reverse) arr.unshift(arr.pop());  else arr.push(arr.shift());  return arr;}

usage:

arrayRotate([1, 2, 3, 4, 5]);       // [2, 3, 4, 5, 1];arrayRotate([1, 2, 3, 4, 5], true); // [5, 1, 2, 3, 4];

If you need count argument see my other answer:
https://stackoverflow.com/a/33451102 🖤🧡💚💙💜

Type-safe, generic version which mutates the array:

Array.prototype.rotate = (function() {    // save references to array functions to make lookup faster    var push = Array.prototype.push,        splice = Array.prototype.splice;    return function(count) {        var len = this.length >>> 0, // convert to uint            count = count >> 0; // convert to int        // convert count to value in range [0, len)        count = ((count % len) + len) % len;        // use splice.call() instead of this.splice() to make function generic        push.apply(this, splice.call(this, 0, count));        return this;    };})();

In the comments, Jean raised the issue that the code doesn't support overloading of push() and splice(). I don't think this is really useful (see comments), but a quick solution (somewhat of a hack, though) would be to replace the line

push.apply(this, splice.call(this, 0, count));

with this one:

(this.push || push).apply(this, (this.splice || splice).call(this, 0, count));

Using unshift() instead of push() is nearly twice as fast in Opera 10, whereas the differences in FF were negligible; the code:

Array.prototype.rotate = (function() {    var unshift = Array.prototype.unshift,        splice = Array.prototype.splice;    return function(count) {        var len = this.length >>> 0,            count = count >> 0;        unshift.apply(this, splice.call(this, count % len, len));        return this;    };})();

I would probably do something like this:

Array.prototype.rotate = function(n) {    n = n % this.length;    return this.slice(n, this.length).concat(this.slice(0, n));}

Edit    Here’s a mutator version:

Array.prototype.rotate = function(n) {    n = n % this.length;    while (this.length && n < 0) n += this.length;    this.push.apply(this, this.splice(0, n));    return this;}