This article is in need of a technical review.
This feature is not on a current W3C standards track, but it is supported on the Firefox OS platform. Although implementations may change in the future and it is not supported widely across browsers, it is suitable for use in code dedicated to Firefox OS apps.
oncfstatechange property specifies an event listener to receive
cfstatechange events. These events occur when the call forwarding state changes.
navigator.mozMobileConnection.oncfstatechange = funcRef;
funcRef is a function to be called when the
cfstatechange event occurs.
Not part of any specification.