The implementation object (the JavaScript reference for the W3C DOMImplementation object) represents, to a limited degree, the environment that

Returns a reference to a newly created virtual W3C DOM Document (not the document node of an HTML document) object.

Returns a reference to a newly created virtual W3C DOM DocumentType object. You can feed the object returned from this method to the DocumentImp

Returns a Boolean true if the browser application supports (i.e., conforms to the required specifications of) a stated W3C DOM module and version.