Creating a Simple REST App in ExpressJS

4 min readMay 21, 2018

Introduction

Express is an open source framework for NodeJS. To understand the requirement of Express let’s look at the following simple example.

Here we look at creating a simple server using NodeJS through its http module.

Creating a Node Server

const http = require('http');const server = http.createServer((req, res) => {
    if (req.url === '/') {
        res.write('Hello World');
        res.end();
    }if (req.url === '/students ') {
        res.write(JSON.stringify(['Mark', 'Sam', 'Diana']));
        res.end();
    }
});server.listen(3000);console.log('Listening on port 3000...');

The Drawback

In a real world application we have to include multiple routes inside the callback function that is passed to createServer. Therefore the code become complex. To avoid this issue ExpressJS Framework is used. This makes the code much easier to read and maintain.

Installing express

For installing express to your app and adding it to the dependencies execute to following command within the project folder.

$ npm install express --save

Creating an express Server

Creating a server in express is very simple. In below example a server created and it listens on port 3000.

const express = require('express');
const app = express();
app.listen(3000,() => console.log('Listening on port 3000...'));

Implementing GET Method — Getting all the Resources

const express = require('express');
const app = express();
app.get('/', (req, res) => {
    res.send('Hello World');
});
app.get('/students', (req, res) => {
    res.send(JSON.stringify(['Mark', 'Sam', 'Diana']));
});
app.listen(3000, () => console.log('Listening on port 3000...'));

Here unlike in the node we do not have to include multiple if statements to handle routes. Express provide us with a structure for handling the routes. Therefore code becomes much cleaner.

Implementing GET Method — Getting a Resource with specific ID

app.get('/students/:id', (req, res) => {
    res.send(req.params.id);
});

In the above example we send a parameter with the URL– id. For simplicity we are not considering fetching data from a database. Just a response is send back to the client with the id parameter that was specified.

E.g. –

http://localhost:3000/students/001

Output - 001

Implementing POST Method — Creating a Resource

const express = require('express');
const app = express();app.use(express.json());const students = [{
        id: 1,
        name: 'Mark'
    },
    {
        id: 2,
        name: 'Sam'
    },
    {
        id: 3,
        name: 'Diana'
    },
];app.get('/students', (req, res) => {
    res.send(students);
});app.post('/students', (req, res) => {
    const student = {
        id: students.length + 1,
        name: req.body.name
    };students.push(student);
    res.send(student);});app.listen(3000, () => console.log(`Listening on port 3000...`));

POST

http://localhost:3000/students

Output –

Implementing PUT Method — Updating a Resource

Let’s consider the same example we used in POST. Now we are defining the put method.

const express = require('express');
const app = express();app.use(express.json());const students = [{
        id: 1,
        name: 'Mark'
    },
    {
        id: 2,
        name: 'Sam'
    },
    {
        id: 3,
        name: 'Diana'
    },
];app.get('/students', (req, res) => {
    res.send(students);
});app.put('/students/:id', (req, res) => {
    const student = students.find(c => c.id === parseInt(req.params.id));
    if (!student) return res.status(404).send('Student not found.');student.name = req.body.name;
    res.send(student);
});app.listen(3000, () => console.log(`Listening on port 3000...`));

Note : 404 — Resource not found.

PUT

http://localhost:3000/students/1

Output — The updated student object is returned. The name Mark has changed to Mathew.

Implementing DELETE Method — Deleting a Resource

In the below example splice method is used remove one object that is located in the given index.

app.delete('/students/:id', (req, res) => {
    const student = students.find(c => c.id === parseInt(req.params.id));
    if (!student) return res.status(404).send('Student not found.');//Delete
    const index = students.indexOf(student);
    students.splice(index, 1);res.send(student);});

DELETE

http://localhost:3000/students/2