Within the script:
var scripts = document.getElementsByTagName("script"),
src = scripts[scripts.length-1].src;
This works because the browser loads and executes scripts in order, so while your script is executing, the document it was included in is sure to have your script element as the last one on the page. This code of course must be ‘global’ to the script, so save src
somewhere where you can use it later. Avoid leaking global variables by wrapping it in:
(function() { ... })();