function isStrictNumeric(myInput) {
    var validCharacters = "0123456789";
    var isNumeric = true;
 
    for (i = 0; i < myInput.length && isNumeric == true; i++) { 
        if (validCharacters.indexOf(myInput.charAt(i)) == -1) {
            isNumeric = false;
        }
    }
   
    return isNumeric;
}

function isNumeric(myInput) {
    var validCharacters = ".0123456789";
    var isNumeric = true;
 
    for (i = 0; i < myInput.length && isNumeric == true; i++) { 
        if (validCharacters.indexOf(myInput.charAt(i)) == -1) {
            isNumeric = false;
        }
    }
   
    return isNumeric;
}

function isValidPhoneNumber(myInput) {
    var phone_filter = /^[2-9][0-9][0-9]\-[1-9][0-9][0-9]\-[0-9][0-9][0-9][0-9]$/;
    return phone_filter.test(myInput);
}

function isValidEmailAddress(myInput) {
    var email_filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
    return email_filter.test(myInput);
}

function isValidZip(myInput) {
    var five_digit_zip_filter = /^[0-9][0-9][0-9][0-9][0-9]$/;
    var ten_digit_zip_filter = /^[0-9][0-9][0-9][0-9][0-9]\-[0-9][0-9][0-9][0-9]$/;
    
    if (five_digit_zip_filter.test(myInput) == true || ten_digit_zip_filter.test(myInput) == true) {
        return true;
    } else {
        return false;
    }
}