Step by step basic set up for an express app

express-app.md

Building REST API with Node

• Create project folder and run npm -y init to set up package.json

• Optional: Set up git git init

• Install express - npm i express

• Create app.js in the root of the project

• Paste following in the same file

  // app.js
  const express = require('express');
  const app = express();
  
  app.get('/', function (req, res) {
    res.send('Hello World');
  });
  
  app.listen(3000);

• Update package.json scripts with a start

  "scripts": {
      "test": "echo \"Error: no test specified\" && exit 1",
  

      "start": "node app.js"

    },
  

• Test it's working - npm start and open localhost:3000 in the browser

• Install nodemon as dev dependency, so that you don't have to restart server on every change: npm i -D nodemon

• Update your scripts in package.json by adding a dev option:

  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node app.js"
  

    "dev": "nodemon app.js"

  }
  

• Create the routes to your resources in a routes folder in the root of the project. For example products will be a products.js file and it can contain the following CRUD endpoints:

  // routes/products.js
  const express = require('express');
  const router = express.Router();
  
  router.get('/', (req, res, next) => {
    res.status(200).json({ message: 'Get all products' });
  });
  
  router.post('/', (req, res, next) => {
    res.status(201).json({ message: 'Create a new product' });
  });
  
  router.get('/:productId', (req, res, next) => {
    const id = req.params.productId;
    res.status(200).json({ message: `Get product with an ID ${id}` });
  });
  
  router.patch('/:productId', (req, res, next) => {
    const id = req.params.productId;
    res.status(200).json({ message: `Update product with an ID of ${id}` });
  });
  
  router.delete('/:productId', (req, res, next) => {
    const id = req.params.productId;
    res.status(200).json({ message: `Delete product with an ID of ${id}` });
  });
  
  module.exports = router;

• Create a new folder in the root of the project named controllers and move the CRUD operations from your routes to a controller module.

  // controllers/products-controller.js
  const getProducts = (req, res, next) => {
    res.status(200).json({ message: 'Get all products' });
  }
  ...
  // create functions for the rest of the rest of teh endpoints
  
  module.exports = {
    getProducts,
    ...
  }

• Use the methods from your controller module in your routes

  // routes/products.js
  ...
  const productsController = require('../controllers/products-controller')
  ...
  router.get('/', (req, res, next) => productsController.getProducts);
  ...

• Use your resource routes (products in this case) in app.js:

  const express = require('express');
  const app = express();
  

  const productRoutes = require('./routes/products');
  
  app.use('/products', productRoutes);

  app.listen(3000);
  

• Add logging - npm i morgan

  const express = require('express');
  const app = express();
  

  const morgan = require('morgan');

  
  const productRoutes = require('./routes/products');
  

  app.use(morgan('dev'));

  
  app.use('/products', productRoutes);
  
  app.listen(3000);
  

• Add error handling - npm i http-errors

  const express = require('express');
  const app = express();
  const morgan = require('morgan');
  

  const createError = require('http-errors');

  
  const productRoutes = require('./routes/products');
  
  app.use(morgan('dev'));
  
  app.use('/products', productRoutes);
  

  // Non existing routes
  app.use((req, res, next) => {
    const error = new createError.NotFound();
    next(error);
  });
  // Error handling
  app.use((error, req, res, next) => {
    res
      .status(error.status || 500)
      .json({ message: error.message || 'Server error' });
  });

  app.listen(3000);
  

• Add body-parser - npm i body-parser

  const express = require('express');
  const app = express();
  const morgan = require('morgan');
  const createError = require('http-errors');
  

  const bodyParser = require('body-parser');

  // Middleware
  app.use(morgan('dev'));
  

  app.use(bodyParser.urlencoded({ extended: false }));
  app.use(bodyParser.json());

• Add allowed CORS

  // Middleware
  app.use(morgan('dev'));
  app.use(bodyParser.urlencoded({ extended: false }));
  app.use(bodyParser.json());
  

  app.use((req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*');
    res.header(
      'Access-Control-Allow-Headers',
      'Origin, X-Requested-With, Content-Type, Accept, Authorization'
    );
    if (req.method === 'OPTIONS') {
      res.header(
        'Access-Control-Allow-Methods',
        'GET, POST, PUT, PATCH, DELETE'
      );
      return res.status(200).json({});
    }
    next();
  });

• Add your resource models