TypeScript patterns: Controller

The next pattern I want to take a look at, that is fundamental to how many JavaScript applications are structured, is the Controller pattern.

There are different definitions for what a Controller is on the client, depending on what framework people are used to working with. As you may know I often recommend not using a framework, but I go with the definition that a controller encapsulates the UI logic for a part of a web page. A common practice is to have controllers take the html element that it works on as the first constructor argument, followed by dependencies (services and other controllers) and possibly an options object. This will resemble what you are likely doing if you are writing eg. an MVC application in ASP.NET MVC or WebAPI. In much the same way, this allows you to pass in dependencies, and keep the controller free of hardcoded dependencies.