function CFormchecker()
{
    this.form = "";
    this.error = false;
    this.error_fields = Array();

    this.check = check;
    this.check_isset = check_isset;
    this.check_length = check_length;
    this.check_pattern = check_pattern;

    function check(form) {
        this.form = form;
        this.error = false;
        this.error_fields = Array();
        for (i=0; i < this.form.elements.length; i++) {
            el = this.form.elements[i];
            if (check = el.getAttribute("formcheck")) {
                switch (method = check.split(':')[0]) {
                    case 'isset':
                        this.check_isset(el);
                        break;
                    case 'length':
                        this.check_length(el, check.split(':')[1]);
                        break;
                    case 'pattern':
                        this.check_pattern(el, check.split(':')[1]);
                        break;
                }
            }
        }

        if (this.error) {
            message = "Bitte überprüfen Sie die folgenden Eingaben:\n";
            for (i=0; i < this.error_fields.length; i++) {
                message += '- ' + this.error_fields[i] + '\n';
            }
            alert(message);
            return false;
        }
        else {
            return true;
        }
    }

    function check_isset(el) {
        if (!el.value || el.value == '') {
            this.error = true;
            this.error_fields[this.error_fields.length] = el.name;
        }
    }
    function check_length(el, length) {
        if (el.value.length < length) {
            this.error = true;
            this.error_fields[this.error_fields.length] = el.name;
        }
    }
    function check_pattern(el, pattern) {
        var reg = new RegExp(pattern);
        if (!reg.exec(el.value)) {
            this.error = true;
            this.error_fields[this.error_fields.length] = el.name;
        }
    }
}