// validates that the field value string has one or more characters in it
function isNotEmpty(elem) {
    var str = elem.value;
    var re = /.+/;
    if(!str.match(re)) {
        alert("Please fill in the required field.");
        return false;
    } else {
        return true;
    }
}
   
//validates that the entry is a positive or negative number
function isNumber(elem) {
    var str = elem.value;
    var re = /^[-]?\d*\.?\d*$/;
    str = str.toString( );
    if (!str.match(re)) {
        alert("Enter only numbers into the field.");
        return false;
    }
    return true;
}
   
// validates that the entry is 16 characters long when
// input field's maxlength attribute is set to 16
function isLen16(elem) {
    var str = elem.value;
    var re = /\b.{16}\b/;
    if (!str.match(re)) {
        alert("Entry does not contain the required 16 characters.");
        return false;
    } else {
        return true;
    }
}
   
// validates that the entry is formatted as an email address
function isEMailAddr(elem) {
    var str = elem.value;
    var re = /^[\w-]+(\.[\w-]+)*@([\w-]+\.)+[a-zA-Z]{2,7}$/;
    if (!str.match(re)) {
        alert("Verify the email address format.");
        return false;
    } else {
        return true;
    }
}

// check if the form is valid
function isValidForm(form) {
	if (isNotEmpty(form.email))
	{
		if (isNotEmpty(form.name))
		{
			if (isNotEmpty(form.company))
			{
				if (isNotEmpty(form.zip))
				{
				}
			}
		}	
	}
}