It is interesting to note that each of the attributes to that <Page.. xml tag are actually setting properties on the Page control that is created when the view is parsed.
To access these control properties in javascript, UI5 has created setter and getter functions in the format set<Property> and get<Property> (capitalise the first letter of the property when accessing this way).
What you would need to do is to get a reference to this Page control object after it has been rendered. This is usually done by giving the control an "id" attribute and setting a unique value. That way, in the corresponding view controller for this view, you can use "this.byId('<myId>')" to grab the object that represents this page.