Purely Functional Web Apps

Are you familiar with the following recipe?

• First define an API and its documentation.
• Then take the API and create its server implementation.
• Then create a client for the same API, but in JavaScript land.
• Then imperatively modify the browser’s DOM in order to allow user to do and see stuff. Sounds about right?

During this talk you will forget about all these things and become a functional web developer. I will show you how to write type-level web APIs, purely functional server and client implementations and how to render things without touching browser’s DOM. The talk is divided into two parts: backend & frontend. The first part of the talk will introduce the concepts behind haskell-servant and we will implement a simple web app backend. Then we will code the app itself using Elm and reactive approach.