purescript-deku

A PureScript web framework for apps that need to be fast.

In anger

• Verity Scheel's snowflow is snowflake-themed work of web-art.
• Verity Scheel's post on parsing implements a full-featured tweening engine to animate rule-based parsing steps.
• Horizontal and Vertical Events is an article that explores some concepts central to Deku with many tryable & editable examples.

Documentation

Here is a guide to building apps with Deku. The guide is written in Deku and its source code can be found here. You should probably start your Deku journey with this guide. It contains everything you need to build a Deku app, from bootstrapping a project to Hello World to a Discord clone!

Indexed documentation for Deku is published on Pursuit. Deku's structure is currently highly decentralized, so it can be tough to know where to look. Here's a small Deku app that acts as a legend for the Pursuit docs.

main :: Effect Unit
main =
  -- `Deku.Toplevel` contains runInBody
  -- and other functions for hydration and SSR
  runInBody myNut
  where
  -- `Deku.Core` contains the `Nut` type, which is the type
  -- of all Deku applications.
  myNut :: Nut
  myNut = 
    -- `Deku.Do`` is the rebindable do context that allows you
    -- to use hooks in Deku
    Deku.do
      -- `Deku.Hooks` contains hooks like `useState`,
      -- `useDyn`, and `useMemoized`
      setCounter /\ counter <- useState 0
      -- `Deku.DOM`, often imported as `D`, contains all DOM elements,
      -- attributes, and event handlers
      D.div
          [
            -- `Deku.Listeners` contains helper functions for various common
            -- listeners like `click` and `keyUp`
            click $ counter <#> add 1 >>> setCounter
          -- `Deku.Attributes` contains helper functions for various common
          -- attributes like `style` and `klass` (an alias for `class`)
          , klass_ "color: crimson;"
          -- `Deku.CSS` contains `render`, which allows you to take `CSS` from
          -- `purescript-css` and use it in a Deku application
          , style_ $ render do
              color (rgb 42 142 242)
              fontWeight bold
          -- `Deku.Attribute` contains constructors for
          -- uncommon and ad hoc `x-` attributes
          , pure (xdata "my-attr" "my-val")
          ]
        [
          -- `Deku.Control` contains all non-element buiding blocks
          -- for applications, including `text` and `<#~>`, which
          -- allows you to switch between elements.
          text (show <$> counter)
        -- `Deku.Pursx` contains the `~~` operator, which allows you to
        -- construct typesafe Deku using plain old html.
        , (Proxy :: _ "<p>Now you're a Deku ~adj~</p>") ~~
            { adj: text
                (counter <#> mod 2 >>> eq 0 >>> if _ then "newb" else "master")
            }
        ]

So, in summary, ignore the voluminous number of modules in Deku (which makes browsing Pursuit difficult) and focus on the modules used in the example above, namely:

• Deku.Toplevel
• Deku.Core
• Deku.Do
• Deku.Hooks
• Deku.DOM
• Deku.Listeners
• Deku.Attributes
• Deku.CSS
• Deku.Attribute
• Deku.Control
• Deku.Pursx

There are a few more modules to be aware of for advanced usage:

• Deku.Lifecycle contains methods for arbitrary side effects to run when the Deku Nuts mount and dismount from the DOM.
• Deku.Pursx.Anonymous contains an experimental pursx syntax that could theoretically be made better by Visible Type Applications. As that feature develops, if the syntax becomes ergonomic, it may supersede the current pursx syntax.
• Deku.Interpret is for folks that wish to build a custom Deku backend. Deku currently supports Single-page applications (the default), static site rendering, and hydrated static site rendering.

Deku is a small codebase. All of the heavy lifting is done via primitives from purescript-hyrule, the documentation of which is also on Pursuit.

Why another web framework?

Deku aims to be:

• fast: it's up to 2x faster than Halogen for a simple Todo MVC app.
• small: the average Deku program tends to be fewer lines of code than its React or Halogen counterparts.
• ssr-friendly: Deku has out-of-the-box server-side rendering capabilities.

What does Deku mean?

Deku is short for "DOMs Emitted as Kan-extended Universals." It is also the tree of Zelda lore and is a Japanese diminutive for a dullard or simpleton.