Embed stream after login

API
2

Embedding Twitch | Twitch Developers Look at: Working with Events. It tells you you can add an event listener.

var embed = new Twitch.Embed('twitch-embed', {
  channel: 'monstercat'
});

embed.addEventListener(Twitch.Embed.AUTHENTICATE, function(user) {
  console.log(user.login + ' just logged in');
});

You an do other things with that user object on authenticate other than logging it to the console you can modify an HTML to display what you need.

document.getElementById(“SOME_ID_OF_A_DIV”).innerHTML = user;