javascript - 如何仅从一个获取请求而不是两个请求中获取响应

Question

这是我的代码，我试图从数据库中获取联系人，然后查询每个联系人的 messageStore 和 contactStore 以获取每个联系人所需的数据。这就是为什么第一个 sql 查询是在 get_info 函数中完成的。但是，如果当我使用 Postman 进行测试时，我必须按两次请求才能获得我想要的正确响应，那么所有代码​​似乎都可以正常工作。

app.get("/", (req, res) => {
    
        function get_info(data, callback){
            
            var sql = `select LEFT(schema_name, 13) AS db_names from INFORMATION_SCHEMA.SCHEMATA 
            WHERE SCHEMA_NAME rLIKE '[0-9]w'`;
            mysqlConnection.query(sql, function(err, results){
                if (err){ 
                throw err;
                }
                //console.log(results); // good
                //stuff_i_want = results;  // Scope is larger than function
                return callback(results);
            });
        }
    
        function get_messageCount(id, callback){
            
            var sql = `select count(*) as messageCount from ${id}messageStore.messages`;
            mysqlConnection.query(sql, function(err, rows){
                if (err){ 
                throw err;
                }
                //console.log(rows); // good
                stuff_i_want2 = rows;  // Scope is larger than function
                return callback(rows);
            });
        }
    
        function get_contactCount(id, callback){
            
            var sql = `select count(*) as contactCount from ${id}contactStore.wa_contacts`;
            mysqlConnection.query(sql, function(err, fields){
                if (err){ 
                throw err;
                }
                //console.log(rows); // good
                stuff_i_want3 = fields;  // Scope is larger than function
                return callback(fields);
            });
        }
    
        function get_dailyMessages(id, callback){
            
            var sql = 'SELECT FROM_UNIXTIME(substr(`timestamp`, 1, 10), \'%Y %M %D\') AS formattedDate,' +
            `COUNT(*) AS receivedMessageCount
            FROM   ${id}messageStore.messages
            GROUP BY formattedDate
            order by formattedDate`;
            mysqlConnection.query(sql, function(err, fields){
                if (err){ 
                throw err;
                }
                //console.log(rows); // good
                stuff_i_want4 = fields;  // Scope is larger than function
                return callback(fields);
            });
        }
      
        var stuff_i_want = '';
        var stuff_i_want2 = '';
        var stuff_i_want3 = '';
        var stuff_i_want4 = '';
        get_info(contacts, function(result){
            stuff_i_want = result;
            //rest of your code goes in here
            for( let i = 0; i < result.length; ++i){
                if(!doneOnce) contacts.push(
                    {
                        contactNumber: result[i].db_names.replace(/\D/g,""),
                        body: []
                    }
                );
                if(i == result.length-1) doneOnce = true;
            }
            
            const numbersInfo = JSON.parse(JSON.stringify(stuff_i_want)); //numbersInfo is alphanumerical
            let contactsInfo = numbersInfo.map(a => a.db_names.replace(/\D/g,"")); //contactsInfo is changed into numerical only
            for( let i =0; i < contactsInfo.length; ++i){
                get_messageCount( contactsInfo[i], function(rows){
                    stuff_i_want2 = rows;
                    //rest of your code
                    objIndex = contacts.findIndex( (obj => obj.contactNumber == contactsInfo[i]));
                    contacts[objIndex].body.push(JSON.parse(JSON.stringify(rows)));
                });
                get_contactCount( contactsInfo[i], function(fields){
                    stuff_i_want3 = fields;
                    //rest of your code
                    objIndex = contacts.findIndex( (obj => obj.contactNumber == contactsInfo[i]));
                    contacts[objIndex].body.push(JSON.parse(JSON.stringify(fields)));
                });
                get_dailyMessages( contactsInfo[i], function(data){
                    stuff_i_want4 = data;
                    //rest of your code
                    objIndex = contacts.findIndex( (obj => obj.contactNumber == contactsInfo[i]));
                    contacts[objIndex].body.push(JSON.parse(JSON.stringify(data)));
                });
                //console.log(contacts);
            }
            res.send(contacts);
        });
        
    });

因此，为了准确地向您展示，这就是我按一次请求后发生的情况。只有我作为蓝图创建的对象数组，将在其上添加数据作为响应发送。 WHereas，当我再次按下 Postman 的请求时，我得到了这个想要的输出。

标签： javascripthttppython-requestscallbackscopes