Exported function returns undefined NodeJS

Question

The function in the model file works successfully. But to know if there is any duplication in the ID during registering and validate it, I made a return statement in the function. and according to the value of x that is assigned to the function (in the controller file) the server will respond.

//Model file
const bodyParser = require('body-parser');
const express = require('express');
const { check, validationResult } = require('express-validator');
const router = require('express').Router();
router.use(express.json());
const urlencoded = bodyParser.urlencoded({ extended: false });
const User = require('../DB/User.js'); //

function create_user(id1, name1, Password1) {
    var user1 = new User({
        id: id1,
        name: name1,
        Password: Password1
    });
    let x;
    user1.save(function(err) {
        if (err) {
            if (err.code == 11000) {
                x = 0;
                console.log('user already exists and x= ' + x);
                return x;
            } else {
                console.log(err);
            }
        } else {
            x = 1;
            console.log('Saved successfully and x =' + x);
            return x;
        }
    })
}
module.exports = create_user;

//Controller file
const bodyParser = require('body-parser');
const express = require('express');
const { check, validationResult } = require('express-validator');
const { x } = require('joi');
const create_user = require('../model/Registration.js');
const router = require('express').Router();
router.use(express.json());
const urlencoded = bodyParser.urlencoded({ extended: false });



router.get('/Registration', function(req, res, next) {
    res.render('Registration', { checker: 0 });
});

router.post('/Registraion/sign_up', function(req, res) {
    let x = create_user(req.body.id, req.body.name, req.body.password);
    console.log('x =' + x);
    if (x == 0) {
        req.body.id.setCustomValidity("This id is already used");
        console.log('this id exsists and x =' + x); //the output here is x= undefined
    } else {
        res.redirect('/Registration');
    }
});

module.exports = router;

Muslem Omar · Accepted Answer · 2020-10-19 08:22:06Z

1

Because user1.save is async and create_user doesn't wait for it to be resolved before returning, so it returns null.

you can solve that using a callback or an async await pattern

try this:

function create_user(id1, name1, Password1, callback) {
    var user1 = new User({
        id: id1,
        name: name1,
        Password: Password1
    });
    let x;
    user1.save(function(err) {
        if (err) {
            if (err.code == 11000) {
                x = 0;
                console.log('user already exists and x= ' + x);
                callback(x);
                return x;
            } else {
                console.log(err);
            }
        } else {
            x = 1;
            callback(x);
            console.log('Saved successfully and x =' + x);
            return x;
        }
    })
}


//Controller file
router.post('/Registraion/sign_up', function(req, res) {
    create_user(req.body.id, req.body.name, req.body.password, function(x) {
      console.log('x =' + x);
      if (x == 0) {
        req.body.id.setCustomValidity("This id is already used");
                console.log('this id exsists and x =' + x); //the output here is x= undefined
            } else {
                res.redirect('/Registration');
            }
        });
});

answered Oct 19, 2020 at 8:22

Muslem Omar

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1 Comment

Abdul Rahman Ahmed Over a year ago

First of all thanks for help, but I've tried it did not work. The function works very well if the ID was unique and the data become saved in the database, and if the ID was duplicated the function doesn't save and that's good. But in both cases, the function returns undefined whether if the ID was duplicated or not, and as i mentioned the function save the data successfully.

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