Create the code to make an in-app voice call

Create an HTML file called index1.html in your project directory.

Add the following code, but make sure you paste the Alice JWT you generated for the user making the call in the earlier step to the USER_JWT constant:

<!DOCTYPE html>
<html lang="en">
    <script src="./node_modules/nexmo-client/dist/nexmoClient.js"></script>
    <form id="call-app-form">
      <h1>Call App from App</h1>
      <input type="text" name="username" value="" />
      <input type="submit" value="Call" />
    <button id="btn-hangup" type="button">Hang Up</button>
      const callAppForm = document.getElementById("call-app-form");
      const btnHangUp = document.getElementById("btn-hangup");
      new NexmoClient({ debug: true })
        .then(app => {
          callAppForm.addEventListener("submit", event => {
            let username = callAppForm.children.username.value;
            app.callServer(username, "app");

          app.on("member:call", (member, call) => {
            btnHangUp.addEventListener("click", () => {
              console.log("Hanging up...");

This is your client application that uses the Client SDK to make a voice call to the destination user (Bob) .

There are several key components to this code:

  1. A simple UI that allows you to enter a username and then click the Call button to make the the in-app call to the specified user (Bob).
  2. Code that logs the user (Alice) into the Client SDK (a JWT is used for authentication) using .login(USER_JWT).
  3. The function to make the call is callServer(username, type), where type in this case is "app", as the destination is the specified user (Bob). > NOTE: Another way to make Voice Calls is with inAppCall(username) which uses peer-peer call functionality. More info on inAppCall()
  4. When a call is made, a button handler is loaded. When the Hang Up button is clicked call.hangUp() terminates the call.