How to display the data stored in MongoDB using Nodejs? - node.js

Question

This is the code I have used to display the data from MongoDB. Getting error as "result is not defined". I have used the ID from MongoDB to display the result. But the stored data is not displayed on a separate page.
const express = require('express');
const app = express();
const ejs = require('ejs');
const assert = require('assert');
const bodyParser = require('body-parser');
const MongoClient = require('mongodb').MongoClient;
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.set('view engine','ejs');
app.set('')
var url = 'mongodb://localhost:27017';
app.get('/form',(req, res)=>{
res.render('form');
});
app.get('/data',(req, res)=>{
MongoClient.connect(url, (err, db)=>{
assert.equal(null, err);
var dbo = db.db("form");
var details = dbo.collection('usertable').find();
details.forEach((data)=>{
if(_id == 5b5ef0b8e0d9c23c2012cef2){
result = item;
return true;
}
})
});
res.render('customerdata',{item: result });
});
I was able to store the data with the below code:
app.post('/form/submit', (req, res)=>{
var item = {
title: req.body.title,
content: req.body.content,
author: req.body.author
};
MongoClient.connect(url, (err, db)=>{
assert.equal(null, err);
var dbo = db.db("form");
dbo.collection('usertable').insertOne(item, (err, result)=>{
assert.equal(null, err);
console.log('Inserted');
db.close();
});
});
res.redirect('/form');
});
app.listen(8080);

Answer 1

I believe you are facing this problem because
you are not referencing the objects inside the details array properly.
you are also not declaring the result object before entering the forEach loop. And this will result in the value of result being undefined.
Inside your forEach loop, each 'data' is an object. And hence you would have to refer to the id as data._id when you are checking it. Similarly data.item when you are trying to assign the value to result.
I have modified the code. This should work.
app.get('/data',(req, res)=>{
MongoClient.connect(url, (err, db)=>{
assert.equal(null, err);
var dbo = db.db("form");
var details = dbo.collection('usertable').find();
var result;
details.forEach((data)=>{
if(data._id == 5b5ef0b8e0d9c23c2012cef2){
result = data.item;
return true;
}
})
});
res.render('customerdata',{item: result });
});

Answer 2

Several things to note:
MongoClient.connect() is asynchronous, but you are calling res.render() synchronously.
Usually you do not want to initiate a connection to MongoDB at each request.
You should probably do dbo.collection('usertable').find().toArray(function(err, items) {...}); to access the data.

Answer 3

find is async, you have to return the result in the find callback, otherwise it's not defined :
app.get('/data',(req, res)=>{
MongoClient.connect(url, (err, db)=>{
assert.equal(null, err);
var dbo = db.db("form");
dbo.collection('usertable').find({}, function(err, details){
if(err)
{
res.render('customerdata',{item: null });
}
else
{
var result = null;
details.forEach((data)=>{
if(data._id.toString() == "5b5ef0b8e0d9c23c2012cef2"){
result = item;
}
})
res.render('customerdata',{item: result });
}
});
});
In addition your post request has the same mistake, your redirecting the user before the end of the insert operation. Correct code is :
app.post('/form/submit', (req, res)=>{
var item = {
title: req.body.title,
content: req.body.content,
author: req.body.author
};
MongoClient.connect(url, (err, db)=>{
assert.equal(null, err);
var dbo = db.db("form");
dbo.collection('usertable').insertOne(item, (err, result)=>{
assert.equal(null, err);
console.log('Inserted');
db.close();
res.redirect('/form');
});
});
});