The icegatheringstatechange event is sent to the onicegatheringstatechange event handler on an RTCPeerConnection when the state of the ICE candidate gathering process changes. This signifies that the value of the connection's iceGatheringState property has changed.

When ICE first starts to gather connection candidates, the value changes from new to gathering to indicate that the process of collecting candidate configurations for the connection has begun. When the value changes to complete, all of the transports that make up the RTCPeerConnection have finished gathering ICE candidates.

This event is not cancelable and does not bubble.

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("icegatheringstatechange", (event) => {});

onicegatheringstatechange = (event) => {};

A generic Event.

This example creates a handler for icegatheringstatechange events.

pc.onicegatheringstatechange = (ev) => {
  let connection = ev.target;

  switch (connection.iceGatheringState) {
    case "gathering":
      /* collection of candidates has begun */
      break;
    case "complete":
      /* collection of candidates is finished */
      break;
  }
};

Likewise, you can use addEventListener() to add a listener for icegatheringstatechange events:

pc.addEventListener(
  "icegatheringstatechange",
  (ev) => {
    let connection = ev.target;

    switch (connection.iceGatheringState) {
      case "gathering":
        // collection of candidates has begun
        break;
      case "complete":
        // collection of candidates is finished
        break;
    }
  },
  false,
);

• WebRTC API
• Signaling and video calling
• WebRTC connectivity
• Lifetime of a WebRTC session