The CompositionEvent() constructor creates a new CompositionEvent object.
new CompositionEvent(type)
new CompositionEvent(type, options)typeA string with the name of the event. It is case-sensitive and browsers set it to compositionstart, compositionupdate, or compositionend.
options OptionalAn object that, in addition of the properties defined in UIEvent(), has the following properties:
data OptionalA string used to initialize the data property of the new CompositionEvent. Browser-generated events set it to the characters generated by the IME composition.
A new CompositionEvent object.
CompositionEvent, the interface of the objects it constructs.