Passing data from a database query with module.export

Question

I query data from a database and want to display it on my site. I decided to outsource my SQL statements into a seperat file called select.js. How can I pass the database data into my routes file and there on my site? Now it's always undefined. If I put the SQL select directly into my route then it works fine.

What I got so far:

select.js


const db = require('./config'); //Connection works 

//KATEGORIEN LADEN
var sql = 'SELECT * FROM Kategorie';
var Kategorie_data;
db.query(sql, function (err, data, fields) {
  if (err) throw err;
  Kategorie_data = data; //tried there playing a bit with the var data
});

module.exports = {
    kategorie_data: Kategorie_data,
}

snippet route.js

var express = require('express');
var router = express.Router();
var db = require('../query/select');

router.get('/api', function (req, res, next) {
    console.log(db.kategorie_data);
    res.render('api/api', {kategorie_data: db.kategorie_data });
});

api.ejs

<% if(kategorie_data.length!=0){
    var i=1;
        kategorie_data.forEach(function(data){
    %>
<%=data.Kategorie_Name %>
<%  i++; }) %>
<% } else{ %>
   No Data Found
<% } %>

Abdul Haseeb · Accepted Answer · 2021-03-02 08:16:05Z

1

select.js

const get_data=()=>{
  var sql = 'SELECT * FROM Kategorie';
  return new Promise((resolve,reject) => {
    db.query(sql, function (err, data, fields) {
      if (err) reject(err);
      resolve({data});
    });
  })
}
module.exports={
  get_data
}

router.js

  router.get('/api', (req, res, next) => {
    db.get_data()
      .then(({ data: kategorie_data }) => {
        res.render('api/api', { kategorie_data });
      })
      .catch((error) => {
        // do your thing
      });
  });

answered Mar 2, 2021 at 8:16

Abdul Haseeb

3721 silver badge6 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Abaddon666 · Accepted Answer · 2021-03-02 08:02:38Z

0

The query function is asynchronous, using a callback. So at the time you create the export Kategorie_data is still undefined. Since the export is cached it is also not updated later on.

You can export a function which will execute the query for you:

var getKategorieData = function (callback){
  db.query(sql, callback);
}


module.exports = {
    kategorie_data: getKategorieData,
}

and then use it like this:

router.get('/api', function (req, res, next) {
    db.kategorie_data((err, data, fields)=>{
       if(error) //error handling
       else {
         res.render('api/api', {kategorie_data: data });
       }
    });
    res.render('api/api', {kategorie_data: db.kategorie_data });
});

answered Mar 2, 2021 at 8:02

Abaddon666

1,63319 silver badges33 bronze badges

Collectives™ on Stack Overflow

Passing data from a database query with module.export

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related