从节点js中的单独文件获取回调

Question

I have two file in my node js app server.js and database.js

//server.js
var db = require('./database.js');

var express = require('express');
var app = express();

var server = app.listen(8081, '000.00.00.000',function(){
    var host = server.address().address;
    var port = server.address().port

    console.log('App listening');

})


app.get('/',function(req,res){
    res.end("Hello Jamian");
})


app.get('/insertuser',function(req,res){
    console.log("insert user called")

    var result = new db.insertUser();
    console.log("result " + result)    
});

and

//database.js
var mysql = require('mysql');

var con = mysql.createConnection({
    host:"localhost",
    user:"0000",
    password:"0000",
    database: "aaaa"
});

con.connect(function(err){
    if(err) throw err;
    console.log("DB Connected");
});

module.exports = {
  insertUser: function () {

    console.log("module exported");

    var SQL_insert_user = "insert into users(username,useremail,usermobile,userpassword,activetoken) values('darren','darren@yahoo.in','980000000','password','ASKDO5615F')";
    con.query(SQL_insert_user,function(err,result){
        if(err) throw err;

        console.log("data inserted");

        return result;
    });
  },
  bar: function () {
    console.log("bar called")
  }
};

I need a callback from the insertUser function in database.js so i can call a res.end("data inserted"). however it seems con.query is going async, hence I am getting a blank value when I try to log result in server.js from get/insertuser in server.js

data inserted
insert user called
module exported
result {}
data inserted

Answer 1

Use promises. Either native or from a library.

Here's how you could do it with a promise:

insertUser: function(){
    return new Promise(function(reject, resolve){
        var SQL_insert_user = "insert into users(username,useremail,usermobile,userpassword,activetoken) values('darren','darren@yahoo.in','980000000','password','ASKDO5615F')";
        con.query(SQL_insert_user,function(err,result){
            if(err) reject(err);
            else resolve(result);
        });
    });
},

Then you can use it your other file like this:

insertUser()
.then(function(result){
    // do something with the result
})
.catch(function(err){
    // Oh no! there was an error!
});

Answer 2

in your server js do

 app.get('/insertuser',function(req,res){ console.log("insert user called") var result = new db.insertUser(function(result) { console.log("result " + result) }); }); 

and in your database do

 module.exports = { insertUser: function (cb) { console.log("module exported"); var SQL_insert_user = "insert into users(username,useremail,usermobile,userpassword,activetoken) values('darren','darren@yahoo.in','980000000','password','ASKDO5615F')"; con.query(SQL_insert_user,function(err,result){ if(err) throw err; console.log("data inserted"); cb(result); }); }, bar: function () { console.log("bar called") } };