mern-todo-backend/src/server.js

import express from 'express'
import bodyParser from 'body-parser'
import cors from 'cors'
import mongoose from 'mongoose'

import Todo from './todo.model'

const app = express()
const PORT = 4000

app.use(cors())
app.use(bodyParser.json())

app.listen(PORT, function () {
    console.log(`Server is running on Port: ${PORT}`)
})

mongoose.connect('mongodb://localhost:27017/todos?authSource=admin', {
    useNewUrlParser: true,
    useUnifiedTopology: true,
    user: "admin",
    pass: "admin"
})

const connection = mongoose.connection

connection.on('error', console.error.bind(console, 'connection error:'))
connection.once('open', function () {
    console.log('Connected successfully to mongodb server')
})

const todoRoutes = express.Router()

app.use('/todos', todoRoutes)

todoRoutes.route('/').get((req, res) => {
    Todo.find((err, todos) => {
        if (err) {
            console.log(err)
        } else {
            res.json(todos)
        }
    })
})

todoRoutes.route('/:id').get((req, res) => {
    let id = req.params.id
    Todo.findById(id, (err, todo) => {
        res.json(todo)
    })
})

todoRoutes.route('/add').post((req, res) => {
    let todo = new Todo(req.body)
    todo.save()
        .then(todo => { res.status(200).json({ 'todo': 'todo added successfully' }) })
        .catch(err => { res.status(400).send('adding new todo failed') })
})

todoRoutes.route('/update/:id').post((req, res) => {
    Todo.findById(req.params.id, (err, todo) => {
        if (!todo) {
            res.status(404).send("data is not found")
        } else {
            todo.todo_description = req.body.todo_description
            todo.todo_responsible = req.body.todo_responsible
            todo.todo_priority = req.body.todo_priority
            todo.todo_completed = req.body.todo_completed

            todo.save()
                .then(todo => res.json('Todo updated!'))
                .catch(err => res.status(400).send("Error while updating"))
        }
    })
})