NodeJS

Crash course 

03

PAY Namibia 2018

ExpressJS

What is it?

- NodeJS framework

- Bunch of useful features

- Fast and productive development

Instalation

npm install express --save

const express = require('express');

let app = express();

app.get('/', (req, res) => {
    res.send('Hello Express')
});

app.listen(process.env.PORT || 3000)

Reading query params

https://localhost:3000?name=Dusan&last=Stankovic

app.get('/', (req,res)=>{
    res.send(req.query);
});

Checkpoint #1

Pass two numbers and operation in query parameters and return value.

E.g.

localhost:3000?operation=sum&a=4&b=10

returns 14

Showing static files

app.use(express.static(__dirname + "/public"));

localhost:3000/public/1.png

Midleware

app.use(express.static(__dirname + "/public"));

a function that has access to request, response and next middleware function. 

app.use((req, res, next) => {
   // do something with req or response

   //call next middleware function 
   next(); 
});    

Checkpoint #2

Pass 4 numbers in a query string and create 4 middlewares doing a basic arithmetic operation.

E.g. for url: localhost:3000?init=1&a=3&b=10&c=2&d=3

should result in: -4

Explanation:

init state = 1; 

1st middleware: 1+3 = 4

2nd middleware: 4-10 = -6

3rd middleware: -6 * 2 = -12

4th middleware: -12/3 = -4

nodeschool.io

npm install -g expressworks