What does the hash (#) mean after a .js file?

Question

what is the significance of the hash (#) here, how does it relate to the .js file:

<script src="foo.js#bar=1"></script>

Answer 1

The hash after the script is used by the embedded script for configuration. For example, have a look at the provided example (facebook):

1. window.setTimeout(function () {
2.    var a = /(connect.facebook.net|facebook.com\/assets.php).*?#(.*)/;
3.    FB.Array.forEach(document.getElementsByTagName('script'), function (d) {
4.        if (d.src) {
5.            var b = a.exec(d.src); //RegExp.exec on the SRC attribute
6.            if (b) {
7.               var c = FB.QS.decode(b[2]); //Gets the information at the hash
8.               ...

In the script, each <script> tag^{line 3} is checked for occurrences^{line 5} of the hash ^{line 2} at the attribute. Then, if the hash exists^{line 6}, the hashdata is extracted^{line 7}, and the function continues.

Answer 2

I doesn't do anything in terms of loading the script. What I am guessing is, the script itself looks for its own script tag, and picks out the piece after the hash (bar=1), and uses it to configure its behavior somehow. To do this, they probably have to loop through all script tags and match against the src attribute.

Answer 3

It is probably used within the referenced .js file reading the raw URL and extracting the parameter (using something window.location, for example and parsing out what is after the #).