Node.js postgreSQL integration - TypeError: Cannot read property 'status' of undefined

Question

I am trying to implement a simple postgresql / Node.JS site however, I am coming across a TypeError with regards to the res object in the query.js file, when performing the query in postgreSQL to insert into a webpage.

I have created a route/users.js file which renders the site and specifies the 'user' variable as such:

const express = require('express');
const router = express.Router();
const request = require('request');
const db = require('../../config/queries');

router.get('/', (req, res, next) =>
  res.render('users', {
    users: db.getUsers
  })
);

module.exports = router;

Then I have a config/queries.js file which performs the query and returns the result to the above file:

const pool = require('./db');

const getUsers = (req, res) => {
  pool.query('SELECT * FROM users ORDER BY id ASC', (error, results) => {
    if (error) {
      throw error;
    }
    console.log(results.rows);
    res.status(200).json(results.rows);
  });
};

module.exports = {
  getUsers
};

Finally the html site is written as such:

<p> Hello world</p>
<ul> {{users}} 99999 </ul>

When I load the page localhost:5000/users, whilst the console is logging the user data correctly, the following error occurs TypeError: Cannot read property 'status' of undefined and the page displays:

Hello world

99999

It appears the error occurs because the res in res.status(200).json(results.rows) is not defined though I don't know why that would be the case.

Many thanks!

Exact duplicate of stackoverflow.com/questions/59277144/…

Bergi
– Bergi

2019-12-14 17:49:38 +00:00
Commented Dec 14, 2019 at 17:49 — Bergi
– Bergi, Commented Dec 14, 2019 at 17:49

BlackBrain · Accepted Answer · 2019-12-14 17:45:40Z

1

You need to modify your code to get results of the query and then try to render the page. getUsers will not return the results immediately but in a callback. So a correct version maybe like this:

router.get('/', (req, res, next) =>

   getUsers((error,result)=>
   {
      if (error) {
          throw error;
      }
      console.log(results.rows);
      res.render('users', {
        users: results.rows
       })
   })
);

const getUsers = (callback) => {
  pool.query('SELECT * FROM users ORDER BY id ASC',callback )
};

answered Dec 14, 2019 at 17:45

BlackBrain

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2 Comments

ewldh20 Over a year ago

Thank you! What is the purpose of "const getUsers = (callback)" ? Beginner question but will help my understanding.

BlackBrain Over a year ago

@ewldh20 it is defining a function getUsers which takes a callback as parameter. it passes that callback to the postgresql , so that when the results are fetched from database the callback is called.

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