Even though JavaScript is a dynamic language, without static or explicit typing declarations and controls, it doesn't mean that you can simply ignore types. Even if the language doesn't allow you to specify the types of your variables or functions, you still work --even if only in your head-- with types. Let's now get into the theme of seeing how we can specify types, for that we will have at least some advantages:
- Even if you don't have runtime data type checking, there are several tools, such as Facebook's flow static type checker or Microsoft's TypeScript language, which let you deal with it
- It will help if you plan to move on from JavaScript to a more functional language such as Elm
- It serves as documentation, to let future developers understand what type of arguments they have to pass to the function, and what type it will return. As an example of this, all the functions in the Ramda library are documented in this way
- It will also help with the functional data structures later...