source: extensions/Piwecard/js/piwecard.js @ 33109

/**
 * Check if a field is valid
 * @param Object element to check
 * @param Integer type of the element (0 is text, 1 is email, 2 is number)
 * @param String Style of the error displayed (default = inline)
 * @param Boolean True if the field can be empty, False otherwise
 * @return True if OK, False otherwise
 */
function piwecard_checkField(element, elementType, display, nullIsOK) {
        var TEXT = 0;
        var EMAIL = 1;
        var NUMBER = 2;
        
        nullIsOK = (typeof nullIsOK === "undefined") ? false : nullIsOK;
        display = (typeof display === "undefined") ? 'inline' : display;
        
        if (nullIsOK && element.value === '') {
                return true;
        } else {
                switch (elementType) {
                        case TEXT:
                                if (element.value == '' || element.className.indexOf("ecard_defaultTextActive") > 0) {
                                        add_error_style(element, display);
                                        return false;
                                } else {
                                        remove_error_style(element);
                                        return true;
                                }
                                break;
                        case EMAIL:
                                var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
                                if (!filter.test(element.value)) {
                                        add_error_style(element, display);
                                        return false;
                                } else {
                                        remove_error_style(element);
                                        return true;
                                }
                                break;
                        case NUMBER:
                                if (element.value == '') {
                                        add_error_style(element, display);
                                        return false;
                                } else {
                                        if (parseFloat(element.value) % 1 == 0){
                                                remove_error_style(element);
                                                return true;
                                        } else {
                                                add_error_style(element, display);
                                                return false;
                                        }
                                }
                                break;
                        default:
                                return false;
                                break;
                }
        }
}

/**
 * Style to add to the field if piwecard_checkField returns false
 * @param Object element
 * @param String Style of the error displayed (default = inline)
 */
function add_error_style(element, display) {
        document.getElementById(element.id+'_error').style.display = display;
        element.className += " ecard_error_input";
}

/**
 * Remove the error style from the field if piwecard_checkField returns true
 * @param Object element
 */
function remove_error_style(element) {
        document.getElementById(element.id+'_error').style.display = 'none';
        element.className = element.className.replace( /(?:^|\s)ecard_error_input(?!\S)/g , '');
}