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;
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