RTCDataChannel: bufferedAmountLowThreshold property

The RTCDataChannel property bufferedAmountLowThreshold is used to specify the number of bytes of buffered outgoing data that is considered "low." The default value is 0. When the number of buffered outgoing bytes, as indicated by the bufferedAmount property, falls to or below this value, a bufferedamountlow event is fired. This event may be used, for example, to implement code which queues more messages to be sent whenever there's room to buffer them. Listeners may be added with onbufferedamountlow or addEventListener().

The user agent may implement the process of actually sending data in any way it chooses; this may be done periodically during the event loop or truly asynchronously. As messages are actually sent, this value is reduced accordingly.

const dc = peerConnection.createDataChannel("File Transfer");
dc.bufferedAmountLowThreshold = 65535;

dc.onbufferedamountlow = () => {
  /* use send() to queue more data to be sent */
};