The source code

    /**
     * @ignore
     *  process form config
     * @author yiminghe@gmail.com
     */
    KISSY.add('ajax/form', function (S, io, DOM, FormSerializer) {

        io.on('start', function (e) {
            var io = e.io,
                form,
                d,
                enctype,
                dataType,
                formParam,
                data,
                tmpForm,
                c = io.config;
            // serialize form if needed
            if (tmpForm = c.form) {
                form = DOM.get(tmpForm);
                enctype = form['encoding'] || form.enctype;
                data = c.data;
                // 上传有其他方法
                if (enctype.toLowerCase() != 'multipart/form-data') {
                    // when get need encode
                    formParam = FormSerializer.getFormData(form);
                    if (c.hasContent) {
                        formParam = S.param(formParam, undefined, undefined, c.serializeArray);
                        if (data) {
                            c.data += '&' + formParam;
                        } else {
                            c.data = formParam;
                        }
                    } else {
                        // get 直接加到 url
                        c.uri.query.add(formParam);
                    }
                } else {
                    dataType = c.dataType;
                    d = dataType[0];
                    if (d == '*') {
                        d = 'text';
                    }
                    dataType.length = 2;
                    dataType[0] = 'iframe';
                    dataType[1] = d;
                }
            }
        });

        return io;

    }, {
        requires: ['./base', 'dom', './form-serializer']
    });