How to create a REST API with Node.js and Express

prerequisites

you must have node installed on your computer. If it isn't the case, go to the official node.js website

you can test your installation in a terminal:

node -v

you should have something like this in return:

v10.3.0

another test? okay. In your terminal, type:

echo console.log("OMG, it works, I can't believe it! OMG!!!!")>test.js

then,

node test.js

and it should print:

OMG, it works, I can't believe it! OMG!!!!

now, delete this file with rm -rf test.js or del test.js, depending on your OS (and if you want to be able to execute unix commands on a window machine, you can install mobaXterm)

initialize the project

create a folder for your project, with mkdir or whatever, then cd to your new folder and type:

npm init

follow the wizard's instructions. You won't need a test command in this tutorial. Indeed, you'd better type:

npm init -y

it will skip the wizard, and write default values in your package.json

install express module

in the root path of your project, type:

npm install express --save

you did it like a boss! 😎

What's a REST API?

A REST API defines a set of functions which developers can perform requests and receive responses via HTTP protocol such as GET and POST. Succint enough?

URI supported by our API

http method	URI	Action
GET	/stuff	lists all the stuff
POST	/stuff	adds new stuff
GET	/stuff/stuffId	prints informations about the stuff which stuff's id is stuffId
PUT	/stuff/stuffId	modifies data about the stuff which stuff's id is stuffId
DELETE	/stuff/stuffId	deletes stuff which stuff'id is stuffId

implementing our API

create a file named index.js (or whatever.js) at the root of your project:

touch index.js

now, open your favourite code editor, and here we go! write this in the js file you created:

// The application requests the use of the Express module.
// The express variable will allow us to use the features of the Express module.
var express = require('express'); 
 
// Here we define the server settings.
var hostname = 'localhost'; 
var port = 3000; 
 
var app = express(); 
 
// start the server
app.listen(port, hostname, function(){
	console.log("Server started on http://"+ hostname +":"+port+"\n"); 
});

Ok, let's give it a try! in the terminal, at the root of your project:

node index.js

it should return

Server started on http://localhost:3000

now, in your browser, go to http://localhost:3000

Oh no, a wild error appears! 😠 It prints Cannot Get / Do you know why, Sherlock? Exactly, we didn't define a get method. let's implement it! 😌

routing management

in index.js again:

// The application requests the use of the Express module.
// The express variable will allow us to use the features of the Express module.
var express = require('express'); 
 
// Here we define the server settings.
var hostname = 'localhost'; 
var port = 3000; 
 
var app = express(); 

// In order to facilitate the routing (the URLs we want to support in our API), we create a Router object.
// It is from this myRouter object that we will implement the methods. 
var myRouter = express.Router(); 
 
// I remind you our URI (/stuff).  
myRouter.route('/stuff')

// let's implement GET, PUT, UPDATE and DELETE methods

    // GET
    .get(function(req,res){ 
        res.json({message : "lists all the stuff", method : req.method});
    })
    //POST
    .post(function(req,res){
        res.json({message : "adds new stuff", method : req.method});
    })
    //PUT
    .put(function(req,res){ 
        res.json({message : "updates a stuff's data", method : req.method});
    })
    //DELETE
    .delete(function(req,res){ 
    res.json({message : "deletes stuff", method : req.method});  
    }); 
 
// We ask our application to use our router method
app.use(myRouter);
 
// start the server
app.listen(port, hostname, function(){
	console.log("Server started on http://"+ hostname +":"+port+"\n"); 
});

now, we can test our API at http://localhost:3000/stuff. If it doesn't work, restart your node server:

• go in the terminal running index.js,
• make ctrl+c
• and again:

node index.js

now it should work. You'll see a JSON like this in your browser (refresh the page): {"message":"lists all the stuff","method":"GET"}