Mozilla DOM Hacking Guide
this is because, if we had a setlocation() method, it would take an nsidomlocation parameter, and not a url string.
...if that is the case, we call nsidomlocation::sethref().
...the default behavior would be that xpconnect expects a nsidomlocation object.
...And 4 more matches

nsIDOMWindowInternal
location nsidomlocation readonly: returns a nsidomlocation object, which contains information about the url of the document.