Express.js

What is Express?

Express.js, or simply Express, is a back end web application framework for building RESTful APIs with Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs. It has been called the de facto standard server framework for Node.js

initialisation:

npm init 

installation of express:

npm install express --save 

installation of nodemon

npm i nodemon

nodemon is a tool that helps develop Node.js based applications by automatically restarting the node application when file changes in the directory are detected.

Run express server on: localhost:3000

send json: localhost:3000/jsonexample

path is a inbuild module
we can call directories

params

The req.params property is an object containing properties mapped to the named route “parameters”. For example, if you have the route /student/:id, then the “id” property is available as req.params.id. This object defaults to {}.
http://localhost:3000/api/products/3

query
The req.query property allows you to access the query parameters from the URL of an incoming HTTP request. Query parameters are key-value pairs included in the URL after the “?” symbol, and they are separated by “&” symbols.
http://localhost:3000/api/v1/query?search=r&limit=2

Basic crud operation
modules

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

//app.use(express.json());

let books is a arr obj

let books = [
    {id:1,title:'Book 1',author: 'author 1'},
    {id:2,title:'Book 2',author: 'author 2'},
]

read

app.get('/', (req, res) => {
    res.json(books)
})

app.use(express.json())

create

app.post('/books', (req, res) => {
    console.log(req.body)
    const newBook = req.body;
    newBook.id = books.length + 1;
    books.push(newBook);
    res.status(201).json(newBook)

})

update/put

app.put('/books/:id',(req, res)=> {
    const id = parseInt(req.params.id)
    const updatedBooks = req.body
    const index = books.findIndex(book => book.id === id);

    if (index !== -1) {
        books[index] = { ...books[index], ...updatedBooks }
        res.json(books[index])
    }
    else {
        res.status(404).json({error: "book not found"})
    }

})

delete

app.delete('/books/:id', (req, res) => {
    const id = parseInt(req.params.id);
    const index = books.findIndex((book) => book.id === id);
    if (index !== -1) {
      const deletedBook = books[index];
      books.slice(index, 1);
      res.json(deletedBook);
    } else {
      res.status(404).json({ error: "book not found" });
    }
})

port

app.listen(3000, () => {
    console.log('server is running on port 3000')
})

but this is not a good way to operate CRUD operations
there is a better way
folder structure

index.js

const express = require('express')
const app = express();
const bookRoutes=require('./routes/bookRoutes')

app.use(express.json());
app.use('/',bookRoutes)

app.listen(3000, () => {
    console.log('server is running on port 3000')
})

bookController.js

let books = [
  { id: 1, title: "Book 1", author: "author 1" },
  { id: 2, title: "Book 2", author: "author 2" },
];

//read
const getBooks=(req, res) => {
  res.json(books);
}

//create
const createBooks= (req, res) => {
  console.log(req.body);
  const newBook = req.body;
  newBook.id = books.length + 1;
  books.push(newBook);
  res.status(201).json(newBook);
}

//update /put
const updateBooks= (req, res) => {
  const id = parseInt(req.params.id);
  const updatedBooks = req.body;
  const index = books.findIndex((book) => book.id === id);

  if (index !== -1) {
    books[index] = { ...books[index], ...updatedBooks };
    res.json(books[index]);
  } else {
    res.status(404).json({ error: "book not found" });
  }
}

//delete
const deleteBooks=  (req, res) => {
  const id = parseInt(req.params.id);
  const index = books.findIndex((book) => book.id === id);
  if (index !== -1) {
    const deletedBook = books[index];
    books.slice(index, 1);
    res.json(deletedBook);
  } else {
    res.status(404).json({ error: "book not found" });
  }
}

module.exports = {
    getBooks,createBooks,updateBooks,deleteBooks
}

bookRoutes.js

const express = require('express')

const bookController = require('../controllers/bookController')

const router = express.Router()

router.get('/books',bookController.getBooks)
router.post('/books',bookController.createBooks)
router.put('/books/:id',bookController.updateBooks)
router.delete('/books/:id', bookController.deleteBooks)

module.exports = router;

check out in github: