Cloact

A simple ClojureScript interface to React.

Cloact provides a way to write efficient React components using (almost) nothing but plain ClojureScript functions.

Examples

Cloact uses Hiccup-like markup instead of React's sort-of html. It looks like this:

(defn some-component []
  [:div
   [:h3 "I am a component!"]
   [:p.someclass 
    "I have " [:strong "bold"]
    [:span {:style {:color "red"}} " and red"]
    " text."]])

You use one component inside another:

(defn calling-component []
  [:div "Parent component"
   [some-component]])

And pass properties from one component to another:

(defn child [props]
  [:p "Hi, I am "
   (:name props)])

(defn childcaller []
  [child {:name "Foo"}])

You mount the component into the DOM like this:

(defn mountit []
  (cloact/render-component [childcaller](.-body js/document)))

assuming we have imported Cloact like this:

(ns readme
  (:require [cloact.core :as cloact]))

The state of the component is managed like a ClojureScript atom, so using it looks like this:

(defn state-ful [props this]
  ;; "this" is the actual component
  [:div {:on-click #(swap! this update-in [:clicked] inc)}
   "I have been clicked "
   (or (:clicked @this) "zero")
   " times."])

State can also be handled using Cloact's version of atom, like this:

(def click-count (cloact/atom 0))

(defn state-ful-with-atom []
  [:div {:on-click #(swap! click-count inc)}
   "I have been clicked " @click-count " times."])

Any component that dereferences a cloact/atom will be automatically re-rendered.

If you want do some setting up when the component is first created, the component function can return a new function that will be called to do the actual rendering:

(defn using-setup [props this]
  (reset! this {:clicked 0})
  (fn [props]
    [:div {:on-click #(swap! this update-in [:clicked] inc)}
     "I have been clicked " (:clicked @this) " times."]))

This way you can avoid using React's lifecycle callbacks like getInitialState and componentWillMount most of the time.

But you can still use them if you want to, either using cloact/create-class or by attaching meta-data to a component function:

(defn plain-component [props this]
  [:p "My html is " (:html @this)])

(def component-with-callback
  (with-meta plain-component
    {:component-did-mount
     (fn [this]
       (swap! this assoc :html
              (.-innerHTML (cloact/dom-node this))))}))

See the examples directory for more examples.

Performance

React is pretty darn fast, and so is Cloact. It should even be faster than plain old javascript React a lot of the time, since ClojureScript allows us to allow a lot of unnecessary rendering (through judicious use of React's shouldComponentUpdate).

The ClojureScript overhead is kept down, thanks to lots of caching.

Code size is a little bigger than React.js, but still quite small. The todomvc example clocks in at roughly 56K gzipped, using advanced compilation.

About

The idea and some of the code for making components atom-like comes from pump. The reactive-atom idea (and some code) comes from reflex.

The license is MIT.