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.
action is a read-only property that indicates what to do with the call forwarding rule.
var action = instanceOfMozMobileCFInfo.action;
Returns a number, whose value is one of the
MozMobileCFInfo.CALL_FORWARD_ACTION_* constant values.
Not part of any specification.