Show the Message History

You want your users to see all the messages in the Conversation. You can achieve this by handling the Conversation’s getEvents method (to retrieve messages sent and received before the current session started) and its text event (which alerts your application when a user sends a message).

In the case where the number of messages are more than the page size of the request, you can use getNext() to receive the next page. More information on getNext() can be found in the documentation. This function is called when the Load Previous Messages button is clicked. Place this code after the loginForm event listener and before the run function.

loadMessagesButton.addEventListener("click", async (event) => {
  // Get next page of events
  let nextEvents = await listedEvents.getNext();
  listMessages(nextEvents);
});

Your application can retrieve the message detail from the event data sent to each handler and add it to the list of messages.

To list the messages, we will create a listMessages function that will take an events page and perform a few steps.

First, if the events page has messages on a following page, the "Load Previous Messages" button is visible. To do that, hasNext() is called and returns a boolean based on if there is another page of messages. You can find out more information about hasNext() in the documentation.

Next, you will loop through the events, format and combine them and then add to the message list.

Add the following code to the bottom of chat.js:

function listMessages(events) {
  let messages = '';

  // If there is a next page, display the Load Previous Messages button
  if (events.hasNext()){
    loadMessagesButton.style.display = "block";
  } else {
    loadMessagesButton.style.display = "none";
  }

  // Replace current with new page of events
  listedEvents = events;

  events.items.forEach(event => {
    const sender = { displayName: event._embedded.from_user.display_name, memberId: event.from, userName: event._embedded.from_user.name, userId: event._embedded.from_user.id };
    const formattedMessage = formatMessage(sender, event, conversation.me);
    messages = formattedMessage + messages;
  });

  // Update UI
  messageFeed.innerHTML = messages + messageFeed.innerHTML;
  messagesCountSpan.textContent = messagesCount;
  messageDateSpan.textContent = messageDate;
}

In this example, you will use the identity of the user to distinguish between messages sent by them and those received from other users by displaying them in a different color. Create a formatMessage function for this, by adding the following code to the bottom of chat.js:

function formatMessage(sender, message, me) {
  const rawDate = new Date(Date.parse(message.timestamp));
  const options = { weekday: "long", year: "numeric", month: "long", day: "numeric", hour: "numeric", minute: "numeric", second: "numeric" };
  const formattedDate = rawDate.toLocaleDateString(undefined, options);
  let text = '';
  messagesCount++;
  messageDate = formattedDate;

  if (message.from !== me.id) {
    text = `<span style="color:red">${sender.userName.replace(/</g,"&lt;")} (${formattedDate}): <b>${message.body.text.replace(/</g,"&lt;")}</b></span>`;
  } else {
    text = `me (${formattedDate}): <b>${message.body.text.replace(/</g,"&lt;")}</b>`;
  }

  return text + "<br />";

}

Now that you have implemented a way to show messages on the page, add the following to the bottom of your run function to load historical messages:

// Update the UI to show which user we are
document.getElementById("sessionName").textContent = conversation.me.user.name + "'s messages"

// Load events that happened before the page loaded
let initialEvents = await conversation.getEvents({ event_type: "text", page_size: 10, order:"desc" });
listMessages(initialEvents);

Finally, you need to set up an event listener for any new incoming messages. You can do this by listening to the conversation.on('text') event. This will also update the messages count. Add the following to the bottom of the run function:

  // Any time there's a new text event, add it as a message
  conversation.on("text", (sender, event) => {
    const formattedMessage = formatMessage(sender, event, conversation.me);
    messageFeed.innerHTML = messageFeed.innerHTML +  formattedMessage;
    messagesCountSpan.textContent = messagesCount;
  });