Logging in to the application

The first interaction with the server is to log in with a unique username. This is to identify ourselves as well as give other users a unique identifier to call us by. To do this, we simply send a name to the server, which will then tell us if the username has been taken or not. In our application, we will let the user select any name they would like.

To implement this, we need to add a bit of functionality to our application's script file. You can add the following to your JavaScript:

var loginPage = document.querySelector('#login-page'),
    usernameInput = document.querySelector('#username'),
    loginButton = document.querySelector('#login'),
    callPage = document.querySelector('#call-page'),
    theirUsernameInput = document.querySelector('#their username'),
    callButton = document.querySelector('#call'),
    hangUpButton = document.querySelector('#hang-up');

callPage.style.display = "none";

// Login when the user clicks the button
loginButton.addEventListener...