in-viewport-5.js

_setupElement: on('didInsertElement', function() {
  if (!canUseDOM) { return; }

  const viewportUseRAF = get(this, 'viewportUseRAF');

  this._setInitialViewport(window);
  this._addObserverIfNotSpying();
  this._setViewportEntered(window);

  if (!viewportUseRAF) {
    forEach(listeners, (listener) => {
      const { context, event } = listener;
      this._bindListeners(context, event);
    });
  }
}),