title: Check if Javascript script exists on page
body: <p>I have a bookmarklet that I've made and it loads a script from my server onto the users current page. However I have an if check in my script that if a condition is not met then no action is taken. However if the user then meets that condition then the code is run, but has caused there to be two sets of scripts inserted into their page. Can i prevent this?</p>
  
  <pre><code> &lt;a href="javascript: (function () {
      var jsCode = document.createElement('script');
      jsCode.setAttribute('src', 'http://xxx.co.uk/xxx/script.js');
    document.body.appendChild(jsCode);
   }());"&gt;Bookmarklet&lt;/a&gt;
  </code></pre>