function getScroll() {
    this.element = ('scroll' in this.valuesEnd) && (!this.element || this.element === window)
      ? scrollContainer : this.element;

    return this.element === scrollContainer
      ? (window.pageYOffset || scrollContainer.scrollTop)
      : this.element.scrollTop;
  }
Returns the current property computed style.
@returns {number} computed style for property