var isJSON=function (str) {

                if (typeof str == 'string') {

                    try {

                        var obj = JSON.parse(str);

                        if (typeof obj == 'object' && obj) {

                            return true;

                        } else {

                            return false;

                        }

                    } catch (e) {

                        console.log('error：' + str + '!!!' + e);

                        return false;

                    }

                }

                console.log('It is not a string!')

            }