Existing Code : Server Code and API routing are in a same file

• This is the code we are going to refactor.
• app.js

    const express = require('express')
    const app = express()
    const port = process.env.PORT
    app.use(express.json())

    // Get Connection Pool
    const pool = require('./config/database');


    // Create Routes
    app.get('/api/users', getAllUsers);
    app.post('/api/users', createUser);

    async function getAllUsers(req,res){    
        const result = await pool.query("select * from users");    
        res.status(200).json(result[0]);
    }

    async function createUser(req,res){
        let user = req.body;
        let params = [ user.name, user.email, user.password, user.role];
        const result = await pool.query("insert into users (name,email,password,role) values ( ?,?,?,?)", params);    
        res.status(201).json({id:result[0].insertId});        
    }

    // Create Commmon Error Handler
    app.use(function (err, req, res, next) {
        console.log("common error handler")
        console.error(err);
        res.status(500).json({errorMessage:err.message});
    })

    app.listen(port, () => console.log(`app listening on port port!`))

Refactoring Task 1: Separate REST API's

• router.js

    const express = require('express');
    const router = express.Router();

    // Get Connection Pool
    const pool = require('./config/database');

     // Create Routes
    router.get('/', (req, res) => res.send('REST API is working!'));
    router.get('/users', getAllUsers);
    router.post('/users', createUser);

    async function getAllUsers(req,res){    
        const result = await pool.query("select * from users");    
        res.status(200).json(result[0]);
    }

    async function createUser(req,res){
        let user = req.body;
        let params = [ user.name, user.email, user.password, user.role];
        const result = await pool.query("insert into users (name,email,password,role) values ( ?,?,?,?)", params);    
        res.status(201).json({id:result[0].insertId});        
    }


    module.exports = router;

• Note: Instead of mapping - /api/users , we can use just /users in router.js ( /api is already added in app.js)

• app.js

    
    const express = require('express')
    const app = express()
    const port = process.env.PORT
    app.use(express.json())

    // Create Routes
    const apiRoutes = require('./router');
    app.get('/api', apiRoutes);
    
    // Create Commmon Error Handler
    app.use(function (err, req, res, next) {
        console.log("common error handler")
        console.error(err);
        res.status(500).json({errorMessage:err.message});
    })

    app.listen(port, () => console.log(`Server is listening on port ${port}!`));