router in express code example

Example 1: express hello world

//to run : node filename.js
const express = require('express')
const app = express()
const port = 3000

app.get('/', (req, res) => res.send('Hello World!'))

app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`))

//visit localhost:3000
// assuming you have done 1) npm init 2) npm install express

Example 2: express router file

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

// middleware that is specific to this router
router.use(function timeLog (req, res, next) {
  console.log('Time: ', Date.now());
  next();
});
// define the home page route
router.get('/', function (req, res) {
  res.send('Birds home page');
});
// define the about route
router.get('/about', function (req, res) {
  res.send('About birds');
});

module.exports = router;

Example 3: app.get

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

const { getElementById, getIndexById, updateElement,
  seedElements, createElement } = require('./utils');

const PORT = process.env.PORT || 4001;
// Use static server to serve the Express Yourself Website
app.use(express.static('public'));

const expressions = [];
seedElements(expressions, 'expressions');
const animals = [];
seedElements(animals, 'animals');

// Get all expressions
app.get('/expressions', (req, res, next) => {
  res.send(expressions);
});

// Get a single expression
app.get('/expressions/:id', (req, res, next) => {
  const foundExpression = getElementById(req.params.id, expressions);
  if (foundExpression) {
    res.send(foundExpression);
  } else {
    res.status(404).send();
  }
});

// Update an expression
app.put('/expressions/:id', (req, res, next) => {
  const expressionIndex = getIndexById(req.params.id, expressions);
  if (expressionIndex !== -1) {
    updateElement(req.params.id, req.query, expressions);
    res.send(expressions[expressionIndex]);
  } else {
    res.status(404).send();
  }
});

// Create an expression
app.post('/expressions', (req, res, next) => {
  const receivedExpression = createElement('expressions', req.query);
  if (receivedExpression) {
    expressions.push(receivedExpression);
    res.status(201).send(receivedExpression);
  } else {
    res.status(400).send();
  }
});

// Delete an expression
app.delete('/expressions/:id', (req, res, next) => {
  const expressionIndex = getIndexById(req.params.id, expressions);
  if (expressionIndex !== -1) {
    expressions.splice(expressionIndex, 1);
    res.status(204).send();
  } else {
    res.status(404).send();
  }
});

// Get all animals
app.get('/animals', (req, res, next) => {
  res.send(animals);
});

// Get a single animal
app.get('/animals/:id', (req, res, next) => {
  const animal = getElementById(req.params.id, animals);
  if (animal) {
    res.send(animal);
  } else {
    res.status(404).send();
  }
});

// Create an animal
app.post('/animals', (req, res, next) => {
  const receivedAnimal = createElement('animals', req.query);
  if (receivedAnimal) {
    animals.push(receivedAnimal);
    res.status(201).send(receivedAnimal);
  } else {
    res.status(400).send();
  }
});

// Update an animal
app.put('/animals/:id', (req, res, next) => {
  const animalIndex = getIndexById(req.params.id, animals);
  if (animalIndex !== -1) {
    updateElement(req.params.id, req.query, animals);
    res.send(animals[animalIndex]);
  } else {
    res.status(404).send();
  }
});

// Delete a single animal
app.delete('/animals/:id', (req, res, next) => {
  const animalIndex = getIndexById(req.params.id, animals);
  if (animalIndex !== -1) {
    animals.splice(animalIndex, 1);
    res.status(204).send();
  } else {
    res.status(404).send();
  }
});

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

Example 4: express route parameters

Route path: /users/:userId/books/:bookId
Request URL: http://localhost:3000/users/34/books/8989
req.params: { "userId": "34", "bookId": "8989" }

Example 5: widlicard in express router

//This route path will match acd and abcd.
app.get('/ab?cd', function (req, res) {
  res.send('ab?cd')
})
//This route path will match abcd, abbcd, abbbcd, and so on.
app.get('/ab+cd', function (req, res) {
  res.send('ab+cd')
})
//This route path will match abcd, abxcd, abRANDOMcd, ab123cd, and so on.
app.get('/ab*cd', function (req, res) {
  res.send('ab*cd')
})
//This route path will match /abe and /abcde.
app.get('/ab(cd)?e', function (req, res) {
  res.send('ab(cd)?e')
})
//This route path will match anything with an “a” in it.
app.get(/a/, function (req, res) {
  res.send('/a/')
})
//This route path will match butterfly and dragonfly, 
//but not butterflyman, dragonflyman, and so on.
app.get(/.*fly$/, function (req, res) {
  res.send('/.*fly$/')
})

Example 6: express mounting router

var express = require('express')
var router = express.Router()

// middleware that is specific to this router
router.use(function timeLog (req, res, next) {
  console.log('Time: ', Date.now())
  next()
})
// define the home page route
router.get('/', function (req, res) {
  res.send('Birds home page')
})
// define the about route
router.get('/about', function (req, res) {
  res.send('About birds')
})

module.exports = router