How to Create A Simple API: ExpressJS

Express JS is a backend framework that runs on Node JS.

It really comes in handy when creating backend microservices for our applications.

I will take you through simple steps in creating a simple API with Express.

Installing dependencies

This should be the simplest of all:

On the project root, open up your terminal/CMD and install express using the following command:

npm install express

Create a server file

While still on the root of your project, create a JavaScript file; app.js

Creating A server:

On the newly created file (app.js), let's create a simple server:

// importing express
const express = require('express')

// creating a instance of express
const app = express();

After bringing express into the app, let's create a simple server:

app.listen(5000, console.log('App Running On Port 5000!'))

The .listen() method binds and listens for connections on the specified host and port.

Your file should now have the following code:

// importing express
const express = require('express')

// creating a instance of express
const app = express();

app.listen(5000, console.log('App Running On Port 5000!'))

On your terminal, run the server using:

node app.js

When you see the message: 'App Running On Port 5000!' on your terminal, well! you are good to GO.

Getting the API

Well normally, your backend application will be sending data to a client site, let's create a simple server.

On the same folder, create a new file "data.js" with the following data:

const colors = [
  {
    color: 'red',
    value: '#f00',
  },
  {
    color: 'green',
    value: '#0f0',
  },
  {
    color: 'blue',
    value: '#00f',
  },
  {
    color: 'cyan',
    value: '#0ff',
  },
  {
    color: 'magenta',
    value: '#f0f',
  },
  {
    color: 'yellow',
    value: '#ff0',
  },
  {
    color: 'black',
    value: '#000',
  },
]

module.exports = colors

let's write the code to server the data from the file from our server:

// getting the data file
const color = require('./data')

// serving data
app.get('/api/colors', (req, res) => {
    res.send(color)
})

First, we bring in the data file and create the route for getting the data.

// importing express
const express = require('express')

// getting the data file
const color = require('./data')

// creating a instance of express
const app = express();

// serving data
app.get('/api/colors', (req, res) => {
    res.send(color)
})

app.listen(5000, console.log('App Running On Port 5000!'))

Run the server and go to http://localhost:5000/api/colors on your browser.

Wasn't that simple!