The third installment of the Advanced Functions programming series delves into the use of Event Handlers in JavaScript, specifically focusing on implementing custom event types within the PubNub platform. Event Handlers enable developers to execute custom logic on messages based on specified criteria and can be categorized into "before publish or fire" and "after publish or fire" event types. The post highlights the use of the "after presence" event type to create a "Welcome Bot" in an Angular 2 messaging application, which processes presence events to greet users. This implementation demonstrates how minimal code and serverless functions can enhance data stream processing and integration with third-party applications. The text also guides readers through setting up PubNub developer keys and configuring the necessary JavaScript and HTML for the application, emphasizing the ease and efficiency of building real-time, interactive applications using these advanced features.