class extends React.Component in CLJS

es6-class.cljs

(defn my-component [props context updater]
  (cljs.core/this-as this
    (js/React.Component.call this props context updater)
    ;; anything else you want to set-up. use goog.object/set on this
    this))

(gobj/extend
  (.. my-component -prototype)
  js/React.Component.prototype)

;; cljs-specific properties on constructor
;; just so (prn my-component) works properly, not actually required
(set! (.-cljs$lang$type my-component) true)
(set! (.-cljs$lang$ctorStr my-component) "MyComponent")
(set! (.-cljs$lang$ctorPrWriter my-component)
  (fn [this writer opt]
    (cljs.core/-write writer "MyComponent")))
(set! (.. component-fn -prototype -constructor) my-component)