title: How to get all tabs and execute javascript on certain tab id in firefox
body: <p>I am trying to build firefox extension which executes script in the tab. It can be easily done in chrome but I didn't find any api to do that in firefox.</p>
  
  <p>Can you guys show me the way ?</p>
  
  <p>My chrome extension code <a href="https://github.com/sbspk/Prepros/blob/master/chrome-extension/scripts/background.js" rel="nofollow">is here on github</a></p>