An HTML element — when specified, the FormData object will be populated with the form's current keys/values using the name property of each element for the keys and their submitted value for the values. It will also encode file input content. A formdata event is fired on the form when the FormData object is created, allowing the form to modify the formdata if necessary.

A submit button that is a member of the form. If the submitter has a name attribute or is an , its data will be included in the FormData object (e.g. btnName=btnValue).