This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
getDefaultAdapter method is used to retrieve the default adapter used to connect the device to third-party Bluetooth devices.
Each time a new adapter is plugged into the device, it becomes the new default adapter. Usually, a Firefox OS device has only one adapter available.
var request = navigator.mozBluetooth.getDefaultAdapter();
Not part of any specification yet. It should be discussed as part of the W3C's System Applications Working Group.