Using jQuery.validate, compare the values of input fields against one another, create notifications based on similarity rules

string_compare_validate.js

$.validator.addMethod("similarity", function(value, element, params){
	var acceptable = .25;
	
	function mush(str){
		str = str.replace(/[ \?|\.|!|\(|\)|\\|\/]/g, '').toLowerCase();
		var arr = [];
		for(var i = 0; i <= str.length - 1; i++){
			arr.push(str[i]);
		}
		return arr.sort();
	}
	function intersection_destructive(a, b)
	{
	  var result = new Array();
	  while( a.length > 0 && b.length > 0 )
	  {  
	     if      (a[0] < b[0] ){ a.shift(); }
	     else if (a[0] > b[0] ){ b.shift(); }
	     else /* they're equal */
	     {
	       result.push(a.shift());
	       b.shift();
	     }
	  }
	
	  return result;
	}
	var $this = $(element);
	$this.parent().siblings().find('[data-type="' + $this.attr("data-type") + '"]').each(function(i,v){
		if($(v).val().length != 0){
			var thisVal = mush($(v).val());
			var fieldVal = mush($this.val());
			var fieldLen = fieldVal.length;
			var diff = intersection_destructive(fieldVal, thisVal);
			console.log(diff.length/fieldLen);
			return acceptable < (diff.length/fieldLen);
		}
	});
	return true;
}, "Unacceptable similarity to another question or answer.");