The → alert box
The alert() method displays an alert box with a specified message and an OK button.
An alert box is often used if you want to make sure information comes through to the user.
Note: The alert box takes the focus away from the current window, and forces the browser to read the message. Do not overuse this method, as it prevents the user from accessing other parts of the page until the box is closed.
alert vs popup
→ Vimeo Fullscreen in einem Popup-Fenster