Textarea Tutorial

Data Binding

Obtain the Text Data

Each RealTimeModel has a object at its root. We created the model with the following data:


We stored the text data we want to collaborate on in the text property. The Model will therefore contain a RealTimeString under the text property. We will need to grab this RealTimeString in order to collaborate. We can obtain the RealTimeString from the text property using the code below. We don't modify any existing files just yet, but we will use this code snippet later on.

// Get a RealTimeString instance from the "text" property of the RealTimeModel
const rts = model.elementAt(["text"]);

Create a Helper Function to Bind the Textarea

We will now create a helper function that takes a RealTimeString and binds it to the textarea. This helper method will create a two-way binding between the textarea and the RealTimeString. We will create this helper method now, and then call it later on. Add the following code to the end of the tutorial.js file.


const textarea = document.getElementById("textarea");
let textEditor;

// Bind the text area to the real time string
function bindTextarea(rts) {
  // Set the initial data, and set the cursor to the beginning of the text area.
  textarea.value = rts.value();
  textarea.selectionStart = 0;
  textarea.selectionEnd = 0;

  // Create the editor utility passing callbacks to bind local events to
  // the RealtimeString.
  textEditor = new HtmlTextCollabExt.CollaborativeTextArea({
    control: textarea,
    onInsert: (index, value) => rts.insert(index, value),
    onDelete: (index, length) => rts.remove(index, length),
    onSelectionChanged: sendLocalSelection

  // Listen to remote events and pass them to the editor utility
  rts.on(Convergence.StringInsertEvent.NAME, (e) => textEditor.insertText(e.index, e.value));
  rts.on(Convergence.StringRemoveEvent.NAME, (e) => textEditor.deleteText(e.index, e.value.length));

Bind the Model to the Textarea

We will now modify the promise callback method that handles the open model, to obtain the RealTimeString from the text property and pass that to the bindTextarea() method we just created. This portion of the code should now look like the below:


Convergence.connectAnonymously(CONVERGENCE_URL, username).then(domain => {
  return domain.models().openAutoCreate({
    collection: "convergence-tutorials",
    id: "textarea",
    ephemeral: true,
    data: {
}).then(model => {
  // New Code
  const rts = model.elementAt(["text"]);
}).catch(error => {


At this point, you should be able to open the index.html in two separate browser tabs and collaboratively edit the text in one text area and see it reflected in the other.

Next, we will add the required logic add shared cursor and selections to the textarea in order to give the user a more intuitive experience.