Question

My bookmarklet consist of a call to a ‘launcher’ script that is inserted into body. As it runs, it inserts in a similar way more scripts (jQuery, the actual application), and a CSS.

Bookmarklet

javascript:(function(){
    var l = document.createElement('script');
    l.setAttribute('type','text/javascript');
    l.setAttribute('src','launcher.js');
    document.body.appendChild(l);
})();

Launcher.js

var s = document.createElement('script');
s.setAttribute('type','text/javascript');
s.setAttribute('src','my actual script');
document.body.appendChild(s);

// I repeat a block like this once per script/css.

The problem is that if the bookmarklet is clicked twice, all the scripts will be inserted again. How can I prevent this behavior?

Answer 1

You can set a property on the window object which is oddly named, so it is unlikely to cause namespace collisions, on the first run only. On subsequent runs, the code will not execute if the property is present:

    javascript:(function(){
      // Test for existence of your weird property
      if (!window.hasOwnProperty('yourWeirdPropertyX774x9ZZYy4')) {

          // Run all your existing code
          var l = document.createElement('script');
          l.setAttribute('type','text/javascript');
          l.setAttribute('src','launcher.js');
          document.body.appendChild(l);

         // Set the flag so this won't run again
         window.yourWeirdPropertyX774x9ZZYy4 = true;
      }  
    })();