function onStartScroll(tweenProp) {
    // checking 0 will NOT add the render function
    if (tweenProp in this.valuesEnd && !KEC[tweenProp]) {
      this.element = ('scroll' in this.valuesEnd) && (!this.element || this.element === window)
        ? scrollContainer : this.element;
      scrollIn.call(this);
      KEC[tweenProp] = function (elem, a, b, v) {
        /* eslint-disable */
        elem.scrollTop = (numbers(a, b, v)) >> 0;
        /* eslint-enable */
      };
    }
  }
* Sets the scroll target.
* Adds the scroll prevention event listener.
* Sets the property update function.
@param {string} tweenProp the property name