Why the javascript doesn't work when click on an another page? [on hold]

For example, when you access this website:

• http://qiang-blog.herokuapp.com/

The first time you can see the AddThis buttons. But when you click the article title, they can't been shown on the detail page. If you refresh the page, you can see the buttons again.

What's the reason? The browser cache? Then how to fix it?