Reading a JSON file in NodeJs - json

Question

I have a small JSON file with this content
{
"users": [
{
"id": 1593,
"name": "Foo Bar"
}
]
}
and I want to read this content by using the filesystem module. So my application looks this
const fs = require('fs');
const express = require('express');
const app = express();
app.get('/users/:id', function (req, res) {
fs.readFile('./userDb.json', 'utf8', function (err, data) {
var json = JSON.parse(data);
var users = json.users;
console.log(users[0].id); // returns 1593
console.log(req.params.id); // returns 1593
var userObj = null;
for(var i = 0; i < users.length; i++){
var currentUser = users[i];
console.log(currentUser.id); // returns 1593
if (currentUser.id === req.params.id) { // this should be fine 1593 === 1593
userObj = currentUser;
break;
}
}
console.log(userObj); // returns undefined
res.render('users', {
user: userObj
});
});
});
app.listen(3000, function () {
console.log('Server running on port 3000');
});
The log will always return 1593, when I pass it as a parameter but when I want to render my handlebars template, the assigned object is null.
userObj is null, even when trying this code
var userObj = users.find(u => u.id === req.params.id);
but I think the database is not wrong. Where did I made a mistake =?

Answer 1

Pretty sure that req.params.id is a String. Try :
const userObj = users.find(u => u.id === Number(req.params.id));
When you have a doubt about it :
console.log(
`First value : ${v1} - ${typeof v1}`,
`Second value : ${v2} - ${typeof v2}`,
);

Answer 2

Please replace
if (currentUser.id === req.params.id)
with
if (currentUser.id == req.params.id)
Since req.params.id is a string and and currentUser.id is a number, they cannot be compared strictly .
However a non-strict comparison should work fine.

Answer 3

console.log(userObj); // returns undefined
is called after the readFile callback, this is an asynchronous non-blocking event!
You have to move your:
res.render('users', {
user: userObj
});
at the end of readFile function