The source code

    /**
     * @ignore
     *  kissy json use json2 or native conditionally
     */
    KISSY.add('json', function (S, J) {

        if (typeof JSON !== 'undefined') {
            J = JSON;
        }

        /**
         * Provide json utils for KISSY.
         * @class KISSY.JSON
         * @singleton
         */
        return S.JSON = {

            /**
             * Parse json object from string.
             * @param text
             * @return {Object}
             */
            parse: function (text) {
                // 当输入为 undefined / null / '' 时，返回 null
                if (text == null || text === '') {
                    return null;
                }
                return J.parse(text);
            },
            /**
             * serialize json object to string.
             * @method
             * @param {Object} jsonObject
             * @return {String}
             */
            stringify: J.stringify
        };
    }, {
        requires: [
            KISSY.Features.isNativeJSONSupported() ? "" : "json/json2"
        ]
    });