on('request') called twice on every request, why?

Question

I have simple node js code that returns a JSON string on UI if promise is successfully resolved, else it with show error on UI.

const server = require('http').createServer();

server.on('request', (request, response) => {

    new Promise(function(resolve, reject) {

        var jsonInput = '{"result":true, "count":42}';

        resolve(JSON.parse(jsonInput));

    }).then((data) => {

      response.end(JSON.stringify(data));

    }).catch((err) => {

      response.end(String(err));

    });

    console.log('received a request');

});

server.listen(8000);

Why the 'received a request' is printed twice? Does browser sends a second request automatically or my code is buggy?

Answer 1

Why the 'received a request' is printed twice?

Most likely, because your browser sent two requests. Chrome does that the first time you connect, for instance, sending first a request for the URL you actually asked for, and also a request for favicon.ico. Look at request.url to see what the requests are for.

For instance, if I take your code and put it in a file, and change the console.log line to:

console.log('received a request: ' + request.url);

When I connect to http://localhost:8000/, I see:

received a request: /
received a request: /favicon.ico