files/en-us/web/api/rtcdatachannel/bufferedamountlow_event/index.md
{{APIRef("WebRTC")}}
A bufferedamountlow event is sent to an {{domxref("RTCDataChannel")}} when the number of bytes currently in the outbound data transfer buffer ({{domxref("RTCDataChannel.bufferedAmount", "bufferedAmount")}}) falls from above to below or equal the threshold specified in {{domxref("RTCDataChannel.bufferedAmountLowThreshold", "bufferedAmountLowThreshold")}}.
This event is not cancelable and does not bubble.
Use the event name in methods like {{domxref("EventTarget.addEventListener", "addEventListener()")}}, or set an event handler property.
addEventListener("bufferedamountlow", (event) => { })
onbufferedamountlow = (event) => { }
A generic {{domxref("Event")}}.
This example sets up a handler for bufferedamountlow to request more data any time the data channel's buffer falls below the number of bytes specified by {{domxref("RTCDataChannel.bufferedAmountLowThreshold", "bufferedAmountLowThreshold")}}, which we have set to 65536. In other words, we'll try to keep at least 64kB of data in the buffer, reading 64kB at a time from the source.
let pc = new RTCPeerConnection();
let dc = pc.createDataChannel("SendFile");
// Replace with your own source object, such as a file handle
let source = null;
dc.bufferedAmountLowThreshold = 65536;
pc.addEventListener("bufferedamountlow", (ev) => {
if (source.position <= source.length) {
dc.send(source.readFile(65536));
}
});
After creating the RTCPeerConnection, this calls {{domxref("RTCPeerConnection.createDataChannel()")}} to create the data channel. Then a listener is created for bufferedamountlow to refill the incoming data buffer any time its contents fall below 65536 bytes.
You can also set up a listener for bufferedamountlow using its event handler property, onbufferedamountlow:
pc.onbufferedamountlow = (ev) => {
if (source.position <= source.length) {
dc.send(source.readFile(65536));
}
};
{{Specifications}}
{{Compat}}