How does facebook detect when a link as been PASTED

Question

Facebook\'s status update input (well, contenteditable div) detects links.

When typing a link it waits until the spacebar is pressed before fetching the URL.

Answer 1

Listen to the keyup event in the field. If the field's content has changed by more than 1 character after one keyup, something has been pasted.

As @epascarello points out, check right click events, too, as the user could be using the context menu.