js遍历表单组合成键值对字符串

        function serializeForm(f) {//参数f为表单这个DOM对象
            var params = '', tmp;
            for (var i = 0; i < f.elements.length; i++) {
                if (f.elements[i].name) {
                    switch (f.elements[i].type) {
                        case 'hidden':
                        case 'password':
                        case 'text':
                        case 'textarea':
                        case 'select-one':
                            params += (params == '' ? '' : '&') + f.elements[i].name + '=' + encodeURIComponent(f.elements[i].value); break;
                        case 'select-multiple':
                            tmp = '';
                            for (var p = 0; p < f.elements[i].options.length; p++)
                                if (f.elements[i].options[p].selected) tmp += (tmp == '' ? '' : ',') + f.elements[i].options[p].value;
                            if (tmp != '') params += (params == '' ? '' : '&') + f.elements[i].name + '=' + encodeURIComponent(tmp); break;
                        case 'radio': case 'checkbox':
                            if (f.elements[i].checked) params += (params == '' ? '' : '&') + f.elements[i].name + '=' + encodeURIComponent(f.elements[i].value); break;
                    }
                }
            }
            return params;
        }