JavaScript Form Validation

<script language="javascript" type="text/javascript" src="validation.js"></script>
<script language="javascript" type="text/javascript">
// Form Validation
val = new Validate();
 
// Enter the list of items that need to be checked:
// example: val.add('firstname','You must enter your first name.');
val.add('product1','Please enter the product you are requesting a price change for');
 
val.addGroup('Price Change 1','product1','Please enter the product you are requesting a price change for');
val.addGroup('Price Change 1','5county1','Please enter your 5 County Number');
val.addGroup('Price Change 1','companycost1','Please enter your Company Cost');
val.addGroup('Price Change 1','retailprice1','Please enter your Retail Price');
val.addGroup('Price Change 1','retailinstalledprice1','Please enter your Retail/Installed Price');
val.addGroup('Price Change 1','cwceprice1','Please enter your 5CW/5CE Price');
 
val.addGroup('Price Change 2','product2','Please enter the product you are requesting a price change for');
val.addGroup('Price Change 2','5county2','Please enter your 5 County Number');
val.addGroup('Price Change 2','companycost2','Please enter your Company Cost');
val.addGroup('Price Change 2','retailprice2','Please enter your Retail Price');
val.addGroup('Price Change 2','retailinstalledprice2','Please enter your Retail/Installed Price');
val.addGroup('Price Change 2','cwceprice2','Please enter your 5CW/5CE Price');
</script>

<form id="form1" name="form1" method="post" action="/php/contact/mail.php" onSubmit="return val.check()">

function Validate() {
	this.itemArray = new Array();
	this.itemGroups = new Object();
	this.add = Validate_Add;
	this.addGroup = Validate_AddGroup;
	this.check = Validate_Check;
}
 
function Validate_Add(formitem,errortext) {
	this.itemArray.push(Array(formitem,errortext));
}
 
function Validate_AddGroup(formgroup,formitem,errortext) {
	if (!isObject(this.itemGroups[formgroup])) this.itemGroups[formgroup] = new Object();
	this.itemGroups[formgroup][formitem] = errortext;
}
 
function Validate_Check() {
	var error_list = new Array();
	var error_string = '';
	var ele;
	for (i=0;i<this.itemArray.length;i++) {
		if (!Validate_CheckTheItem(this.itemArray[i][0] + '_0_value'))	error_list.push(this.itemArray[i][1]);
 
	}
	if (error_list.length > 0) {
		for (i=0;i<error_list.length;i++) {
			error_string += ' - ' + error_list[i] + '\n';
		}
	}
	for (var theGroup in this.itemGroups) {
		// Determine if the group is "active" or not
		// If one item in the group has content, all must have content
		var GroupIsActive = false;
		var tmpErrors = new Array();
		for (var theItem in this.itemGroups[theGroup]) {
			if (Validate_CheckTheItem(theItem + '_0_value')) {
				GroupIsActive = true;
			}
			else {
				tmpErrors.push(this.itemGroups[theGroup][theItem]);
			}
		}
		if ((GroupIsActive) && (tmpErrors.length > 0)) {
			error_string += '\nIn the '+theGroup+' group:\n';
			for (i=0;i<tmpErrors.length;i++) {
				error_string += ' - ' + tmpErrors[i] + '\n';
			}
		}
	}
 
 
	if (error_string != '') {
		alert('Please correct the following errors:\n'+error_string);
		return false;
	}
 
	else return true;
}
 
 
function Validate_CheckTheItem(itemName) {
 
	ele = document.getElementById(itemName);
	if (ele) {
		if ((ele.value == '') || (ele.value == null)) {
			return false; //error_list.push(this.itemArray[i][1]);
		}
	}
	else {
		ele = document.getElementsByName(itemName);
		if (ele.length > 0) {
			if (ele.length == 1) {
				if ((ele[0].value == '') || (ele[0].value == null)) {
					return false; //error_list.push(this.itemArray[i][1]);
				}
			}
			else {
				have_selected_item = false;
				for (j=0;j<ele.length;j++)	if (ele[j].checked) have_selected_item = true;
				if (!have_selected_item) return false; //error_list.push(this.itemArray[i][1]);
			}
		}
	}
	// If we made it this far...
	return true;
}
 
 
function isObject(a) {
    return (a && typeof a == 'object') || isFunction(a);
}
function isFunction(a) {
    return typeof a == 'function';
}