This API is available on Firefox OS for internal applications only.
Summary
The onussdreceived property specifies an event listener to receive ussdreceived events. These events occur whenever a new USSD message is received.
Note: MozMobileConnection inherits from the EventTarget interface, so it's also possible to listen for events by using the addEventListener() method.
Syntax
navigator.mozMobileConnection.onussdreceived = funcRef;
Where funcRef is a function to be called when the ussdreceived event occurs.
Specification
Not part of any specification.