Request body is empty in Express route - node.js

Question

I am building an API with Node.js, Express.js, and MongoDB. When I submit the form and use the req object in the route, the req.body object is empty.
req.body returns {} when I call the get_user function through the browser using postman at https://localhost:3000/users/0.
app.js:
var express = require('express'),
app = express(),
port = process.env.PORT || 3000,
bodyParser = require('body-parser');
var mongo_server = require('./server')
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));
var routes = require('./routes/users')
routes(app);
app.use(function(req, res) {
res.status(404).send({url: req.originalUrl + ' not found'});
});
app.listen(port);
mongo_server.mongo_connection
module.exports = app;
userController.js:
var mongoose = require('mongoose'),
user = mongoose.model('users');
exports.get_user = function(req, res) {
console.log(req.body.id);
user.findById(req.body.id, function(err, user) {
console.log(req.body);
if(err)
res.send(err);
res.json(user);
});
};
userRoutes.js:
module.exports = function(app) {
var users = require('../controllers/userController');
app.route('/users/:userid')
.get(users.get_user);
}

Answer 1

I think you're confusing request parameters and request bodies. A request body is when you send information with the request like a payload, such as in a POST request when you send JSON to the server to, for example, create a new user:
{
"username": "jd123",
"email": "jd#example.com",
"name": "John Doe"
}
But in your case, you're looking for parameters, things passed through the URL like you've set up:
/users/:userid
That allows you to navigate to with a GET request:
/users/0
And then you can get the 0 as a string from req.params.userid not req.body.id. Request parameters and bodies are different. Parameters are for navigating to a varying route such as a user profile page, where the URL varies and reflects which route you want to go to by a user's ID.
Bodies are used for the payload of a request such as POSTing, PATCHing, and PUTing, giving information on what to update or create on the server.