Detect keypresses interacting with the browser's autocomplete menu

I have a jquery.keypress on a text input, and keypresses that are interacting with the browser's autocomplete are all firing the event. Is there a way to tell if (for instance) enter was hit in the input as opposed to in its autocomplete dropdown?

From stackoverflow

• Use a hidden input field in your form and check to see if it is set to determine if the form was submitted.