Express Cheatsheet: GET (route params & query string) + POST (request body)

m2-express-cheatsheet-GET-POST.md

Intro

Here's some ways of passing information from a client to a server:

• In the URL:

  • Route Params (ex. https://localhost:3000/artists/madonna)
  • Query String (ex. https://localhost:3000/search?maxPrice=200)

• In the BODY of the http request:

  • With some http request methods (for example, POST and PUT), it is possible to send additional data in what is called the "request body".

URL: Route Params

• Example URL:

  • https://localhost:3000/artists/madonna

• How to use route params in Express:

  • In your route's path: define the name for the params you expect

    app.get('/artists/:artistname/', (req, res) => {
        
    });

  • Now we can get the info from req.params...

    app.get('/artists/:artistname/', (req, res) => {
        console.log(req.params); //req.params is an object
        const artist = req.params.artistName;
    });

• Note: it is also possible to define multiple params. For example:

  app.get('/artists/:artistname/albums/:albumName', (req, res) => {
      const artist = req.params.artistName;
      const album = req.params.albumName;
  });

URL: Query String

• Example URL:

  • https://localhost:3000/search?maxPrice=120

• How to use query string in Express

  • Read from the object req.query

  • For example, if we receive a request GET https://localhost:3000/search?maxPrice=120

    app.get('/search', (req, res) => {
        console.log(req.query); // req.query is an object
        const price = req.query.maxPrice;
    });

• Note: we can also pass multiple options in the query string:

  • For example, if we receive a request GET https://localhost:3000/search?maxPrice=120&location=berlin

    app.get('/search', (req, res) => {
        const price = req.query.maxPrice;
        const location = req.query.location;
    });

Request Body

• Data is sent in the 'body' of the http request (also called 'payload').

• How to read data from the body in Express

  1. We need to configure the package body-parser (no need to install since it comes with Express):

      const bodyParser = require('body-parser');
      
      // ...
      
      app.use(bodyParser.urlencoded({ extended: true }));

  2. Then we can read data from the object req.body

  app.post('/login', (req, res) => {
      console.log(req.body)
      if(req.body.email === 'bob@bob.com'){
          //...
      }
  })