mergeSort

function merge(left, middleLeft, middleRight, right) {
	if (left < middleLeft)
		merge(
			left,
			Math.floor((left + middleLeft) / 2),
			Math.floor((left + middleLeft) / 2) + 1,
			middleLeft
		);
	if (middleRight < right)
		merge(
			middleRight,
			Math.floor((middleRight + right) / 2),
			Math.floor((middleRight + right) / 2) + 1,
			right
		);
	mergeItems(left, middleLeft, middleRight, right);
}
function mergeItems(left, middleLeft, middleRight, right) {
	var tempArray = [];
	var indexOfTempArray = 0;
	var leftInit = left,
		rightInit = right;

	while (left <= middleLeft && middleRight <= right)
		if (array[left] > array[middleRight])
			tempArray[indexOfTempArray++] = array[middleRight++];
		else tempArray[indexOfTempArray++] = array[left++];

	while (left <= middleLeft) 
	  tempArray[indexOfTempArray++] = array[left++];
	while (middleRight <= right)
		tempArray[indexOfTempArray++] = array[middleRight++];
		
	for (var iter = leftInit, iterTemp = 0; iter <= rightInit; ++iter, ++iterTemp)
		array[iter] = tempArray[iterTemp];
}
var array = [5, 4, 3, 2, 1, 0];
merge(
	0,
	Math.floor(array.length / 2),
	Math.floor(array.length / 2) + 1,
	array.length - 1
);

console.log(array);