Node.js confusing output from each loop

Question

I'm wondering if someone can help me understand the following behaviour. If I have an app.js file on a node.js server such as below: ``` var http = require('http'); var _ = require('underscore'); http.createServer(function(request, response) { var x = ''; _.each([1, 2, 3], function(num){ x +=" underscore.js says " + num; }); response.writeHead(200, { 'Content-Type': 'text/html' }) response.end(x); }).listen(3000, null); ``` Then everytime I request the page, I see the text "underscore.js say x" 3 times. I expect this as there are 3 numbers in the loop and x is reset on every request. However, if I have the following (x moved outside of callback for createServer): ``` var http = require('http'); var _ = require('underscore'); var x = ''; // Note x is moved outside the createserver callback http.createServer(function(request, response) { _.each([1, 2, 3], function(num){ x +=" underscore.js says " + num; }); response.writeHead(200, { 'Content-Type': 'text/html' }) response.end(x); }).lis…

Accepted Answer

This is probably a disappointing answer, but still.

Your browser will be making a HTTP request to `/favicon.ico`, which will be hitting your script and adding an additional 3 lines to your `x` variable for each request.

- You refresh your page and see 3 lines.

- Your browser requests `/favicon.ico`, and 3 additional lines are added

- You refresh the page, and see 6 lines + the 3 additional.

- Your browser requests `/favicon.ico`, and 3 additional lines are added

... etc.

You'll be able to fix this by checking the `request.url` parameter for ending in `favicon.ico`;

```
if (/\/favicon.ico$/.test(request.url)) {
    // don't incremement
}
```

... or you can do it more funk-ily with the `url()` module;

```
if (require('url').parse(request.url).pathname === '/favicon.ico') {
    // don't incremement.
}
```

Node.js confusing output from each loop

Solution

Problem