Treehouse: Grow your CSS skills. Land your dream job.

Last updated on:

PageVisibility API

<!DOCTYPE HTML>  
 <html>  
 <head>  
      <script type="text/javascript">  
           timer = 0;  
           function onLoad(){  
                document.addEventListener("visibilitychange",stateChanged);  
                document.addEventListener("webkitvisibilitychange", stateChanged);  
                document.addEventListener("msvisibilitychange", stateChanged);  
           }  
           function stateChanged(){  
                console.log(document.webkitVisibilityState);  
                if(document.hidden || document.webkitHidden || document.msHidden){  
                     //new tab or window minimized
                     timer = new Date().getTime();  
                }  
                else {  
                     alert('You were away for ' + (new Date().getTime()-timer)/1000+ ' seconds.')  
                }  
           }  
      </script>  
 </head>  
 <body onLoad="onLoad()">  
 </body>  
 </html>

Demo by Sagar Ganatra

Comments

  1. Trent Ellingsen
    Permalink to comment#

    Seems like this would be handy for browser games. Could pause the game if you change tabs or minimize the window.

Leave a Comment

Posting Code

We highly encourage you to post problematic HTML/CSS/JavaScript over on CodePen and include the link in your post. It's much easier to see, understand, and help with when you do that.

Markdown is supported, so you can write inline code like `<div>this</div>` or multiline blocks of code in in triple backtick fences like this:

```
<script>
  function example() {
    element.innerHTML = "<div>code</div>";
  }
</script>
```