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October 4, 2021 07:56 am GMT

Build Simple Node Js API: no external package

Raw Node:

Frameworks like Express Js or Kao Js have made writing APIs a lot easier. Nonetheless, it is expedient that a developer knows how to write code from the ground up using the in-built module like os, fs, and so on.

Let's start

Create a file app.js.

Import the fs and url modules

const fs = require ('fs');const url = require('url');const http = require('http');

Next, in the sample app.js we create a server.

const server = http.createServer((req,res)=> {    console.log('puppies are friendly...')    res.end('puppies are friendly...');});

The next main thing is to listen to a server

server.listen(3001, '127.0.0.1', ()=> {    console.log('server is running on port 3001');});

The moment of truth. Now let's run node app from our terminal

Visit any browser (in my case, Fire ...) and test your endpoint.

     127.0.0.1:3001

You also get a console log response.

Routing

Let's create multiple endpoints using the url module. As it is, any endpoint/resource we hit will get returned to back to the home page.

To make this work we use the >url> module.

const server = http.createServer((req,res)=> {    const endPoint= req.url;        if(endPoint === '/' || endPoint === '/dogs'){            res.end('This is the puppy landing page');        } else if (endPoint === '/adopt-a-puppy') {            res.end('Adopt our cute puppies');            } else {                res.end('... 404!!!, page not found');        }     });

Writing Headers and Status Code

Let's write headers and responses, i.e., what kind of response are we sending, either html/text or application/json

const server = http.createServer((req, res) => {    const endPoint = req.url;    if (endPoint === '/' || endPoint === '/dogs') {        res.end('This is the puppy landing page');    } else if (endPoint === '/adopt-a-puppy') {        res.end('Adopt our cute puppies');    } else {        res.writeHead(404, {            'Content-type': 'text/html',            'drsimple-header': 'no puppies response'        });        res.end('... 404!!!,  Page not found');    }});

Let's test again

Reading data with fs module (asynchronously).

Next, we will create data.json and read all registered puppies . Here, we will set our Content-type to application/json

const server = http.createServer((req, res) => {    const endPoint = req.url;    if (endPoint === '/' || endPoint === '/dogs') {        res.end('This is the puppy landing page');    } else if (endPoint === '/adopt-a-puppy') {        fs.readFile('./data.json', 'utf-8', (err, data) => {            const puppyData = JSON.parse(data)            res.writeHead(200, {                'Content-type': 'application/json',                'drsimple-header': 'no puppies response'            });            res.end(data)        })    } else {        res.writeHead(404, {            'Content-type': 'text/html',            'drsimple-header': 'no puppies response'        });        res.end('... 404!!!,  Page not found');    }});

Result

Now let's check our developer console, network tab to be specific. (On windows, hit f12)

In the picture above, you can see the 200 status code, which means OK. Just to confirm if our headers went through...double click on the 200 status code. Here you will see the headers I wrote deliberately and the content type.