Clear a modal Form on cancel or close selection

HI

I am trying to work out how to clear a from in a Modal if the user clicks a “Cancel” button (which closes the modal) or the Close icon X.

I thought it might be as simple as having an onclick event to reset the form but it doesn’t seem to work. I assume it is closing the modal before it has time to clear the forms contents?

Can anyone throw me in the right direction?

Cheers!