Every time you load a new page with Turbolinks only the body of the page is replaced. This means that the JavaScript environment stays the same and any variables you've set will remain the same. Sometimes this is actually welcome behaviour as I posted previously about caching dynamic partials but sometimes you want to reset those variables since the context has changed on the new page load.

Resetting JavaScript variables

A simple work around is to just delete the variable and set it again using the Turbolinks page:load event or in a script loaded by the new page. This is the method I use for the tweet links at the bottom of my posts.

delete tweet;
var tweet = function () {
  var left = (screen.width/2)-(600/2);
  var top = (screen.height/2)-(300/2);
  window.open(
    "https://twitter.com/share?via=andruu&text=Check out #{page.title}&url=#{page_url(page.slug)}",
    "Tweet Post", "width=600,height=300,top="+top+",left="+left+""
  );
  return false;
}

You will see that I actually call delete tweet; before I set the variable. If I didn't do this the tweet variable would be set to function the first time it was called and would remain the same after loading a new page.