[Node] Basic

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Creating a Node Server

Core modules:

  • http: launch a server, send request
  • https: launch a SSL encrypted server
  • fs: file system
  • path: constructing apths
  • os
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// app.js
const http = require('http');

function rqListener(req, res) {
    // receive two arguments: request, response
    // Will run for every request that reaches the server
}
http.createServer(rqListener); // Execute rqListener function for every incoming request. 

// OR use anonymous function
const server = http.createServer((req, res) => {
    // process.exit() could kill the event loop of node
})

server.listen(3000); // Let nodejs listen to port 3000

Sending response

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const server = http.createServer((req, res) => {
    res.setHeader('Content-Type', 'text/html');
    res.write('<html>');
    res.write('<p>Helllo</p>');
    res.write('/<html>');
    res.end();
})

Routing Request

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const fs = require('fs');

const server = http.createServer((req, res) => {
    const url = req.url;
    const method = req.method;

    if (url === '/') {
        res.write('<html>');
        res.write('<head><title>Enter Message</title></head>');
        res.write('<body><form action="/message" method="POST"><input type="text" name="message"><button type="submit">Send</button></form></body>');
        res.write('/<html>');
        return res.end();
    }
    
    if (url === '/messasge' && method === 'POST') {
        const body = []
        req.on('data', chunk => {
            // receives a chunk of data
            body.push(chunk);
        });
        req.on('end', () => {
            // when all chunks are precessed
            const parsedBody = Buffer.concat(body).toString();
            const message = parsedBody.split('=')[1];
            fs.writeFile('message.txt', message, (err) => {
                res.statusCode = 302;
                res.setHeader('Location', '/');
                return res.end();
            });
        })
    }
    res.setHeader('Content-Type', 'text/html');
    res.write('<html>');
    res.write('<head><title>My First Page</title></head>);
    res.write('<body><h1>Hello from my Node.js Server!</h1></body>');
    res.write('</html>');
    res.end();
});

server.listen(3000);