mkdir nisim
cd nisim
npm init -y
npm install express

index.js

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

app.listen(5000, () => {
	console.log(`server listen to port 5000`);
});

Port in a variable

const express = require('express');
const app = express();
const PORT = 5000;

app.listen(PORT, () => {
	console.log(`server listen to port ${PORT}`);
});

Add End Point

two arguments:

  • route string
  • callback
app.get('/nisim', (req, res) => {
	// handler
});

just send status code

app.get('/whatever', (req, res) => {
	res.sendStatus(500);
});

Set Response

app.get('/king', (req, res) => {
	res.status(200);
	res.send('avi biter');
});

json method

app.get('/king', (req, res) => {
	res.status(200)
	res.json({
		fname: 'avi',
		lname: 'biter'
	});
});

Chaining

status method return the request object

app.get('/king', (req, res) => {
	res.status(200).json({
		fname: 'avi',
		lname: 'biter'
	});
});

without setting the status it’s going to be 200 by default

download method

let’s say I have an image avi.png in the project directory

app.get('/king', (req, res) => {
	res.download('img/avi.png');
});

End Point With A Variable

http://localhost:5000/singers/first
http://localhost:5000/singers/second
http://localhost:5000/singers/third

Params

const singersMap = new Map([
	['first', 'Elvis Presly'],
	['second', 'Michael Jackson'],
	['third', 'Avi Biter']
]);

app.get('/singers/:nth', (req, res) => {
	const nth = req.params.nth;
	const singerName = singersMap.get(nth);
	res.send(singerName);
});

validation

app.get('/singers/:nth', (req, res) => {
	const nth = req.params.nth;
	const singerName = singersMap.get(nth);

	if (!singerName) {
		res.status(404)
			.send('unknown singer key');
		return;
	}

	res.status(200).send(singerName);
});

number parameter

const singers = [
	'Elvis Presly',
	'Michael Jackson',
	'Avi Biter'
];

app.get('/singers/:index', (req, res) => {
	const index = parseInt(req.params.index);
	const singerName = singers[index];
	res.status(200).send({ name: singerName });
});

validate

in the handler

const index = parseInt(req.params.index);

if (!index && index !== 0) {
	res.status(404).send('not a number');
	return;
}

const singerName = singers[index];

if (!singerName) {
	res.status(404).send('unknown index');
	return;
}

res.status(200).send(singerName);

Post request adding new record

app.post('/singers', (req, res) => {
	const singerName = req.body.singerName;
	singers.push(singerName)
	res.status(200).send(`${singerName} added to db`);
});

Problem

TypeError: Cannot read properties of undefined

Reason

Express does not parse json in body by default

Solution

set up middleware that tells Express to parse json before our handler receive the request

app.use(express.json());

app.post('/singers', (req, res) => {
	const singerName = req.body.singerName;
	singers.push(singerName)
	res.status(200).send(`${singerName} added to db`);
});

Static Route

create directory called public

| index.js | public | pages | nisim.html | shlomo.html | david.html | img | chad1.png | chad2.png | |

app.use(express.static('public'));

http://localhost:5000/pages/nisim.html
http://localhost:5000/pages/shlomo.html
http://localhost:5000/pages/david.html
http://localhost:5000/img/chad1.png
http://localhost:5000/img/chad2.png

Client of the server

  • browser for get methods
  • js (fetch function)
  • curl command
  • vscode extension
  • insomnia/postman applications

curl

curl -X POST http://localhost:5000/singers \
	-H 'Content-Type: application/json' \
	-d '{"singerName":"shimi tavori"}'

REST Client (vscode extension)

@baseUrl = http://localhost:5000

POST {{baseUrl}}/singers
content-type: application/json

{
    "singerName": "shimi tavori"
}

insomnia