ouzdev / express.js-web-api

Step by step creating web app with Express.js 🚀

Web Api sample with Express.Js

Project Goals

• Create a basic web app with Express.js
• Manage a request lifecycle with Middleware
• Json Web Token (JWT) usage with Express.js

Create a basic web app with Express

• Create a file app.js
• Go to terminal, and enter 'npm init -y'. This command creates a default package.json file for your node.Js project.
• In the terminal, enter 'npm install express'. This command installs the Express Framework.
• Open the package.json. In the dependencies section, there is an express entry. This entry means that Express Framework is isntalled.

Create a web app that return JSON data

Add the following code to app.js

app.get("/products",(req,res) => {

    const products = [
    {
        id:1,
        name:"Product 1"
    },
    {
        id:2,
        name:"Product 2"
    }
    ];
    res.json(products);
})

Make sure the app.json that files look like this

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => res.send('Hello World!'));
app.get("/products",(req,res) => {

    const products = [
    {
        id:1,
        name:"Product 1"
    },
    {
        id:2,
        name:"Product 2"
    }
    ];
    res.json(products);
});
app.listen(port, () => console.log(`Example app listening on port ${port}!`));

Manage a request lifecycle with middleware

The Express Framework has built-in support for handling a request in this way.

Add the following code to app.js

const express = require('express')
const app = express()
const port = 3000

app.get('/', (req, res) => res.send('Hello World!'))

app.get('/users',(req,res) => {
  res.json([{
    id: 1,
    name: 'User Userson'
  }])
})

app.get('/products', (req, res) => {
  res.json([{
    id: 1,
    name: 'The Bluest Eye'
  }])
})

app.listen(port, () => console.log(`Example app listening on port ${port}!`))

Create a new file is client.js. Add the following code to client.js

const http = require('http');

http.get({
  port: 3000,
  hostname: 'localhost',
  path: '/users',
  headers: {}
}, (res) => {
  console.log("connected");
  res.on("data", (chunk) => {
    console.log("chunk", "" + chunk);
  });
  res.on("end", () => {
    console.log("No more data");
  });
  res.on("close", () => {
    console.log("Closing connection");
  });
});

Run app.js with node app.js command in terminal.

After that command that run command.

Run client.jsnode client.js command in terminal.

The terminal should look like this.

For app.js

Example app listening on port 3000!

For client.js

connected
chunk [{"id":1,"name":"User Userson"}]
No more data
Closing connection

That from step later open app.js. After the row const app = express(). Add the following code.

function isAuthorized(req,res, next) {
    const auth = req.headers.authorization;
    if (auth === 'secretPassword') {
      next();
    } else {
      res.status(401);
      res.send('Not permitted');
    }
  }

Locate that part of the code.

app.get('/users', (req,res) => {
  res.json([{
    id: 1,
    name: 'User Userson'
  }])
})

Replace part of the code

app.get('/users',isAuthorized, (req,res) => {
  res.json([{
    id: 1,
    name: 'User Userson'
  }])
})