PureScript: Tomorrow’s JavaScript Today by Kris Jenkins

An interesting look at the value proposition of PureScript.

What I found really interesting here were the function signatures because they afford you so much by merely glancing at them, especially when your code has side effects. Here’s the example the presenter uses:

-- Pure
  summariseDocument :: String -> String
  -- Needs network
  fetchDocument :: DocumentId -> Eff (ajax :: AJAX) String
  -- Needs a browser
  renderDocument :: String -> Eff (dom :: DOM) ()
  

This lets you keep track of what pieces of your code can run by themselves and which require other systems (servers, databases, etc) in order to run.

[PureScript] takes you to the future of large scale front-end code reliability. [Now I’ve written systems in PureScript] and every one of those systems in recent years has needed a little bit of JavaScript. Maybe five to ten percent of the codebase is JavaScript. All of my bugs, all of my runtime exceptions, all of my problems, come from that five to ten percent. The rest [of the codebase] is rock solid. I worry about logical errors but I don’t worry about the reliability of my code anymore on the front-end.