The MediaStreamTrackEvent interface represents events which indicate that a MediaStream has had tracks added to or removed from the stream through calls to Media Stream API methods. These events are sent to the stream when these changes occur.
The MessagePort interface of the Channel Messaging API represents one of the two ports of a MessageChannel, allowing sending of messages from one port and listening out for them arriving at the other.
The MouseEvent interface represents events that occur due to the user interacting with a pointing device (such as a mouse). Common events using this interface include click, dblclick, mouseup, mousedown.
The NetworkInformation interface provides information about the connection a device is using to commuinicate with the network and provides a means for scripts to be notified if the connection type changes. The NetworkInformation interfaces cannot be instantiated. It is instead accessed through the connection property of the Navigator interface.
The OfflineAudioContext interface is an AudioContext interface representing an audio-processing graph built from linked together AudioNodes. In contrast with a standard AudioContext, an OfflineAudioContext doesn't render the audio to the device hardware; instead, it generates it, as fast as it can, and outputs the result to an AudioBuffer.
The OscillatorNode interface represents a periodic waveform, like a sine wave. It is an AudioNode audio-processing module that causes a given frequency of sine wave to be created — in effect, a constant tone.
A PannerNode always has exactly one input and one output: the input can be mono or stereo but the output is always stereo (2 channels); you can't have panning effects without at least two audio channels!
The Path2D interface of the Canvas 2D API is used to declare paths that are then later used on CanvasRenderingContext2D objects. The path methods of the CanvasRenderingContext2D interface are present on this interface as well and are allowing you to create paths that you can retain and replay as required on a canvas.