docs: function ScrollToggle(el, config) {
    this.el_ = el;
  
    this.config_ = objects.clone(config);
    if (this.el_.hasAttribute('data-ak-scrolltoggle')) {
      var elConfig = JSON.parse(this.el_.getAttribute('data-ak-scrolltoggle'));
      if (elConfig && typeof elConfig === 'object') {
        objects.merge(this.config_, elConfig);
      }
    }
  
    // Initialize the current scroll position.
    this.lastScrollPos_ = 0;
    this.onScroll();
  }