Get height to the document top after scroll and set set to top

getScrollTop.js

var getScrollTop = function() {
	if(_isMobile) {
		return _mobileOffset;
	} else {
		return window.pageYOffset || documentElement.scrollTop || body.scrollTop || 0;
	}
};

var setScrollTop = function(top, force) {
	_forceRender = (force === true);

	if(_isMobile) {
		_mobileOffset = Math.min(Math.max(top, 0), _maxKeyFrame);
	} else {
		window.scrollTo(0, top);
	}

	return _instance;
};