This API is available on Firefox OS for internal applications only.
Summary
The messageCount property indicates how many messages are available within the voicemail inbox. However, some voicemail indicators will only specify that messages are waiting, but not the actual number. In that case, the value of messageCount will be -1 to indicate that the number of messages is unknown.
Syntax
var count = instanceOfMozVoicemailStatus.messageCount
Value
Return a number
Specification
Not part of any specification yet.