How to take token for chat's conversation?

I do not think you are fully understanding the OAuth handshake process.

Since you appear to be creating a client side application you want to to use the OAuth Implicit Code Flow.

The general process is as follows:

  1. User opens your application and clicks Login and is directed to: https://api.twitch.tv/kraken/oauth2/authorize?client_id=<your client ID>&redirect_uri=http://localhost:3000/public/chatbot.html&response_type=token&scope=chat_login
  2. User accepts the OAuth request via their browser and is redirected back to your application at the redirect_uri
  3. The app access token will be in the URL hash: http://localhost:3000/public/chatbot.html#access_token=XXXXXXX&scope=chat_login
  4. You pull the access_token from the hash and then pass it to your IRC connection logic.