You don't need script tags when using the application.js file. It is already in a .js file. Script tags would be used if you were embedding the script within some html.
You also don't need html tags in a .js file...
The application.js is called from HTML else ware, and is automatically loaded in your app.
So, simply put your code in the application.js file:
function toggle_visibility(id) {
var e = document.getElementById(id);
if(e.style.display == 'block')
e.style.display = 'none';
else
e.style.display = 'block';
}
