Mergesort.js

function mergesort(input){
	if(input.length === 1)
		return input;
		
	var input1 = mergesort(input.slice(0, input.length/2));
	var input2 = mergesort(input.slice(input.length/2));
	
	return merge(input1, input2);
}

function merge(input1, input2){
	
	var merged = [];
	
	while(input1.length && input2.length){
		if(input1[0] <= input2[0]){
			merged.push(input1.shift());
		}else{
			merged.push(input2.shift());
		}
	}
	
	while(input1.length){
		merged.push(input1.shift());
	}
	
	while(input2.length){
		merged.push(input2.shift());
	}
	
	return merged;
}

var test = [1 , 5, 8 ,10, 45, 100, -5];
console.log(mergesort(test));