Preventing duplicate rows in a tabular HTML form

tabular-forms.js

$().ready(function() {
	
	// Save the current value of a select when it gains focus, to
	// be used in case the value is changed.
	$("table select").live('focus', function(){
		$(this).data('oldVal',$(this).val());
	});
	
	//After changing a value in any row,
	$("table select").live('change',function() {

		//get a list of the values in that row
		var values = [];
		$(this).closest("tr").find("input,select,textarea").each(function() {
			values.push($(this).val());
		});
		
		//and then go through all rows
		var matchCount = 0;
		$(this).closest("tbody").find("tr").each(function(){
			
			//and see if those values are there.
			var match = true;
			for (var i = 0; i < values.length; i++) {
				var currVal = $(this).find("td:nth-child("+(i+1)+")").find("input,select,textarea").val();
				match = match && (values[i]==currVal);
			}
			if (match) matchCount++;
		});
		
		// If we find more than one instance of them,
		if (matchCount > 1) {
			
			//tell the user
			$(this).effect("highlight", {color:"#ff0000"}, 800);
			
			//and return the changed value to what it was before.
			$(this).val($(this).data('oldVal'));
		}

	});

});
// For more information, please see http://samwilson.id.au/2011/07/12/tabular-forms/