Observer Pattern Using JavaScript We will use JavaScript to see one simple implementation of the Observer Pattern. I will be using Node.js for JavaScript execution. by Introduction The observer pattern is simply a publish/subscribe relationship. Like a person of interest, we have an object of interest, which we call subject or publisher, and then we have interested parties, and these parties are called observers or subscribers. The subject has something to say, and observers are there interested in that saying. When we arrange our code in this way, code not only becomes easy to read, reason about but also less coupled.