Respo: a virtual DOM library in ClojureScript

Respo: a Virtual DOM library in ClojureScript.

Create elements in Clojure syntax:

(div {:class-name "demo"
      :style {:color :red
              :font-size 16
              :font-family "Josefin Sans"}
      :on-click (fn [event dispatch! mutate!])})

; respo.core/div

Nest child elements:

(div {}
  (span {})
  (div {}))

; respo.core/span

Add text nodes:

(div {}
  (<> "text")
  (<> "text with style" {:color :red}))

; respo.core/<>

Create Components

To define components, use defcomp, which is a Macro:

(defcomp comp-demo [p1 p2]
  (div {}
    (<> p1)
    (<> p2)))

(comp-demo :a :b)

; respo.core/defcomp

Use render! to mount a component. It also handles re-rendering if mounting already happened.

(defonce *store (atom {}))
(defn dispatch! [op op-data] (swap! *store assoc :a 1))

(render! mount-target (comp-container @*store) dispatch!)

; respo.core/render!

To hot replace app code, use render! function. clear-cache! for restting internal rendering caches:

(defn reload! []
  (clear-cache!)
  (render! mount-target (comp-container @*store) dispatch!))

; respo.core/clear-cache!

Adding Effects

Define effect with defeffect macro. You may also compare arguments with old one to decide what to do:

(defeffect effect-focus [a] [action el *local at-place?]
  (when (= :mount action)
    (.focus (.querySelector el "input"))))

Pass component results in a vectors with effects defined:

(defcomp comp-draft [data]
  [(effect-focus data)
   (div {}
      (input {})))]

The effect will be called during with action in :mount :before-update :update and unmount.

Respo would compare [data] passed to effect-focus with old arguments and updates will be called when they change.

States Management

Respo uses an Atom to maintain global states. Global states and "Single Source of Truth" are preferred:

(defonce *store (atom {}))
(defn dispatch! [op op-data] (swap! *store assoc :a 1))

(add-watch *store :changes
           (fn []
               (render! mount-target (comp-container @*store) dispatch!)))

Respo has supports for component-level states. But states is designed in an awkward syntax in order to make sure it's consistent with "Single Source of Truth". Read about mutate! and cursor-> in the docs.

Ecosystem

During developing Respo, a bunch of libraries are added:

ui -- basic UI styles collected based on Flexbox

markdown -- subset Markdown syntax rendering to virtual DOM

message -- displaying message on top-right corner

feather -- icons library of feather

alerts -- replacing alert/confirm/prompt components

router -- HTML5 router library decoupled from view part

reel -- time travelling developing tool

value -- to display collections

form -- simple form library

notifier -- notification notifier

You may also try Reacher which is a React wrapper.

Try Respo

Now it's your turn to read Guide and try Respo:

Read guides

Browse examples

Try minimal Respo app by your own

For Advanced developers, probably the best way to understand Respo is to read code of how the author is using it. Contact me on Twitter anytime if you got questions.

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