create web-component v1 in cljs without class

web-component-v1.cljs

(defn component []
  (js/Reflect.construct js/HTMLElement #js [] component))

(set! (.-prototype component)
  (js/Object.create (.-prototype js/HTMLElement)
    #js {:connectedCallback
         #js {:configurable true
              :value
              (fn []
                (this-as this
                  (js/console.log "connected" this)))}

         :disconnectedCallback
         #js {:configurable true
              :value
              (fn []
                (this-as this
                  (js/console.log "disconnectedCallback" this)))}

         :attributeChangedCallback
         #js {:configurable true
              :value
              (fn []
                (this-as this
                  (js/console.log "attributeChangedCallback" this)))}

         }))

(js/window.customElements.define "x-component" component)

(let [x (js/document.createElement "x-component")]
  (js/document.body.appendChild x))