Change Mode - JavaScript

In a live stream, audience members usually join in RECV_ONLY mode, meaning they can only view and listen to the hosts. However, if a host invites an audience member to actively participate (e.g., to speak or present), the audience member can switch their mode to SEND_AND_RECV using the changeMode() method.

This guide explains how to use the changeMode() method and walks through a sample implementation where a host invites an audience member to become a host using PubSub.

note

This page uses the following asynchronous methods. Refer to their API reference for the errors each Promise may reject with, and handle these rejections appropriately based on your use case.

• changeMode()
• publish()
• subscribe()

changeMode()

• The changeMode() method allows a participant to switch between modes during a live stream—for example, from audience to host.

Example

let liveStream;

// Initialize Live Stream
liveStream = VideoSDK.initMeeting({
  // ...
});

const changeModeBtn = document.getElementById("changeModeBtn");
changeModeBtn.addEventListener("click", async () => {
  // Changing Mode
  try {
    await liveStream?.changeMode("SEND_AND_RECV");
  } catch (err) {
    console.error("changeMode failed:", err);
  }
});

Implementation Guide

Step 1 : Create a Pubsub Topic

• Set up a PubSub topic to send a mode change request from the host to a specific audience member.

// Create a topic for the participant
const topic = `REQUEST_TO_JOIN_AS_HOST_${participantId}`;

// Publish function
async function invitePublish(message) {
  try {
    await liveStream?.pubSub.publish(topic, message);
  } catch (error) {
    console.log("Error while publishing REQUEST_TO_JOIN_AS_HOST:", error);
  }
}

Step 2 : Create an Invite Button

• Add an "Invite on Stage" button for each audience member. When clicked, it publishes a PubSub message with the mode "SEND_AND_RECV" to that participant.

const participants = liveStream.participants;
const participant = participants.get("<participant-id>");
const mode = participant ? participant.mode : null;

// Define the topic
const topic = `REQUEST_TO_JOIN_AS_HOST_${participantId}`;

// Publish function to send the request
async function invitePublish(message) {
  try {
    await liveStream?.pubSub.publish(topic, message);
  } catch (error) {
    console.log("Error while publishing REQUEST_TO_JOIN_AS_HOST:", error);
  }
}

// Handle request
function handleRequest() {
  invitePublish({ mode: "SEND_AND_RECV" });
}

// Render a button if the mode is "RECV_ONLY"
const container = document.createElement("div");

if (mode === "RECV_ONLY") {
  const container = document.createElement("div"); // Container for the button

  const button = document.createElement("div");
  button.innerText = "Invite on Stage";
  button.style.cursor = "pointer"; // Make the button look clickable
  button.onclick = handleRequest;

  container.appendChild(button);

  // Append the container to the body (or specific container)
  document.body.appendChild(container);
}

Step 3 : Create a Listener to Change the Mode

• On the audience side, subscribe to the specific PubSub topic. When a mode request is received, update the participant’s mode using changeMode().

const topic = `REQUEST_TO_JOIN_${mMeeting?.localParticipant?.id}`;
const listeners = {
  onMessageReceived: async ({ message }) => {
    if (message && message.mode) {
      try {
        await liveStream.changeMode(message.mode);
      } catch (err) {
        console.error("changeMode failed:", err);
      }
    }
  },
};
try {
  await liveStream.pubSub.subscribe(topic, listeners);
} catch (error) {
  console.log("Error while subscribing to REQUEST_TO_JOIN:", error);
}

note

Calling changeMode() changes only the caller's mode. Every other client must rebuild its host and audience lists from the participant-mode-changed event, as described in Updating the UI on mode change.

Updating the UI on mode change

changeMode() updates the mode of the participant who calls it. The room then broadcasts a participant-mode-changed event to every participant, including clients that did not initiate the change. Each client should use that event to update its UI.

In the event handler, rebuild the lists that drive your UI by filtering participants by their current mode, then refresh the view. Simply pinning, unpinning, or displaying a message is not enough: when a participant is promoted, their mode changes, but other clients will not automatically move them from the audience to the stage.

meeting.on("participant-mode-changed", (data) => {
  const { participantId, mode } = data;
  // Re-derive both lists from meeting.participants, then re-render.
  renderSpeakers();
  renderViewers();
});

caution

Rebuild both lists — the speakers and the viewers. Removing the participant from the audience list alone is the common half-fix: they disappear from the audience and never appear on stage.

API Reference

The API references for all the methods and events utilized in this guide are provided below.

• changeMode()
• PubSub