Nodejs web server calling requestListener twice when page is loaded

Problem

The following is the example web server from the documentation, with an added counter. It prints the counter to the console whenever a client/browser requests the page.

However, it’s being called twice when requested by the browser. Why?

This is what I would expect would happen:

browser : Hello World 1
console : Counter 1
[reload page]
browser : Hello World 2
console : Counter 2

but this happens:

browser : Hello World 1
console : Counter 1
Counter 2
[reload page]
browser : Hello World 3
console : Counter 3
Counter 4

I run the code using the command line

$ node example.js

Here is the code:

var 
http = require('http'),
counter = 0,
sys = require('util');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
counter++;
res.end('Hello World ' + counter + '\n');
sys.puts('Counter ' + counter);
}).listen(8000, "");

Problem courtesy of: Garrows

Solution

In programming, when stuck, it’s always handy to trace the code to better understand what’s happening. The easiest way to do this is to put more debug/print statements in till you can see what’s going on.

Change the sys.puts line to:

sys.puts('Counter ' + counter + " from " + req.url);

I think you’ll find that the 2nd request is the browser requesting the favicon for the site.

Solution courtesy of: bxjx

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