check diffrence between two arrays

getdiff.js

/*
 * creator: Danj (https://github.com/DanBrothers)
 * description: check diffrence between two arrays
 * license: MIT, please link to this if you copy (thanks)
 *
 * usage:
 	//returns array of diffrences
 	diff(arrayone, arraytwo);
 	
 	//can also be used to check two files, by creating two arrays of the two files
 	//check for every line
 	diff(file1text.split("/n"), file2text.split("/n"));
 */

//this function is to sort the two arrays for easy use
function diff(a1, a2){
	var matrix = new Array(a1.length+1);
	
	for(var y=0; y<matrix.length; y++){
		matrix[y] = new Array(a2.length+1);
		
		for(var x=0; x<matrix[y].length; x++){
			matrix[y][x] = 0;
		}
	}
	
	for(var y=1; y<matrix.length; y++){
		for(var x=1; x<matrix[y].length; x++){
			if(a1[y-1]===a2[x-1]){
				matrix[y][x] = 1 + matrix[y-1][x-1];
			} else {
				matrix[y][x] = Math.max(matrix[y-1][x], matrix[y][x-1]);
			}
		}
	}
	
	try {
		//loop thru array and return new matrix
		return getDiff(matrix, a1, a2, x-1, y-1, new Array());
	} catch(e){
		alert(e);
	}
}

//this function is to get the diffrence between two
function getDiff(matrix, a1, a2, x, y, newmatrix){
	//check if there is a difference
	if(x>0 && y>0 && a1[y-1]===a2[x-1]){
		// the two values are the same
		// continue in the array
		getDiff(matrix, a1, a2, x-1, y-1, (newmatrix[x-1] = a1[x-1]));
	} else {
		if(x>0 && (y===0 || matrix[y][x-1] >= matrix[y-1][x])){
			// a2 contains one more item then a1
			// continue in the array
			getDiff(matrix, a1, a2, x-1, y, (newmatrix[x-1] = a2[x-1]));
		} else if(y>0 && (x===0 || matrix[y][x-1] < matrix[y-1][x])){
			// a1 contains one more item then a2
			// continue in the array
			getDiff(matrix, a1, a2, x, y-1, (newmatrix[y-1] = a1[y-1]));
		} else {
			//there are no new items, so return the new matrix
			return newmatrix;
		}
	}
	
}