_observerCallback()

in applications/clouddemo/net4/CloudDemo.Mvc/Scripts/bootstrap.bundle.js [6379:6418]

• 28 lines of code
• 9 McCabe index (conditional complexity)

    _observerCallback(entries) {
      const targetElement = entry => this._targetLinks.get(`#${entry.target.id}`);

      const activate = entry => {
        this._previousScrollData.visibleEntryTop = entry.target.offsetTop;

        this._process(targetElement(entry));
      };

      const parentScrollTop = (this._rootElement || document.documentElement).scrollTop;
      const userScrollsDown = parentScrollTop >= this._previousScrollData.parentScrollTop;
      this._previousScrollData.parentScrollTop = parentScrollTop;

      for (const entry of entries) {
        if (!entry.isIntersecting) {
          this._activeTarget = null;

          this._clearActiveClass(targetElement(entry));

          continue;
        }

        const entryIsLowerThanPrevious = entry.target.offsetTop >= this._previousScrollData.visibleEntryTop; // if we are scrolling down, pick the bigger offsetTop

        if (userScrollsDown && entryIsLowerThanPrevious) {
          activate(entry); // if parent isn't scrolled, let's keep the first visible item, breaking the iteration

          if (!parentScrollTop) {
            return;
          }

          continue;
        } // if we are scrolling up, pick the smallest offsetTop


        if (!userScrollsDown && !entryIsLowerThanPrevious) {
          activate(entry);
        }
      }
    }