Preference-based authentication - Tools?

function getstring()
{
var nlike = 2; // minimum number of likes required
var ndislike = 2 ; // minimum number of dislikes r
var str1 = ""; // represents the combinational string of images selected  
var str2 = str1;
var div1 = document.getElementsByClassName('like');  
var div2 = document.getElementsByClassName('dislike');  
if(div1.length >= nlike && div2.length >= ndislike)
{
	for(var i=0; i<div1.length; i++) { 
		if(i!= div1.length -1)
		{
		 str1 += div1[i].id+ ",";  
		}
		else
		{
		str1 += div1[i].id;
		}
	}
	
	for(var i=0; i<div2.length; i++) { 
		if(i==0)
		{
		  str1 += "@"+div2[i].id;  
		}
		else if(i== div2.length -1)
		{		
			str1 += ","+div2[i].id;  
		}
		else
		{
			str1 += ","+div2[i].id;  
		}
	}
	document.getElementById('dk').value=str2;  
	document.getElementById('lk').value=str1;  
	document.forms["myform"].submit();  
	//alert("Liked Images: "+str1+"\nDisliked Images: "+str2); 
	
}