unable to run an external javascript using a bookmarklet

Question

Totally newbie about JS.

I need to use an external script which modifies some elements in the current page accessing it as a bookmarklet.

If I modify the htm

Answer 1

A common practice is to simply use a self-executing function expression, something like this:

(function () {
  var s=document.createElement('script');
  s.type='text/javascript';
  s.src='script.js';
  document.getElementsByTagName('head')[0].appendChild(s);
}());

Bookmarklet:

javascript:(function(){var s=document.createElement('script');s.type='text/javascript';s.src='script.js';document.getElementsByTagName('head')[0].appendChild(s);}());

The function will return undefined (no return value supplied) preventing the navigation.

Note also that this will avoid creating global variables (like s) that can overlap with other variables used on the page, because all variables are created in the scope of the anonymous function.