//test if null or empty
function isNullOrEmpty(value)
{
	return (value == null || value == '');
}

//test if single digit
function isDigit(value)
{
    //one occurance of a digit
    var regex = /^\d{1}$/;
    return regex.test(value);
} 

//test if number
function isNumber(value)
{
    //One or more occurances of a digit
    var regex = /^[0-9]+$/;
    return regex.test(value);
}

function validateQuoteBox()
{
	var result = true;
	var zipcode = document.getElementById('zipcode');	
	
	if(isNullOrEmpty(zipcode.value))
	{
		result = false;
		alert('Please enter a zip code');		
	}
	else if( !isNumber(zipcode.value) || zipcode.value.length != 5 )
	{
		result = false;
		alert('Please enter a valid zip code');
	}	
	
	return result;
}