Interface UnderlyingSource<R>

A function that is called whenever the consumer cancels the stream, via stream.cancel(), defaultReader.cancel(), or byobReader.cancel(). It takes as its argument the same value as was passed to those methods by the consumer.

A function that is called whenever the stream’s internal queue of chunks becomes not full, i.e. whenever the queue’s desired size becomes positive. Generally, it will be called repeatedly until the queue reaches its high water mark (i.e. until the desired size becomes non-positive).

A function that is called immediately during creation of the ReadableStream.