code: function getOffset(element) {
    var box = element.getBoundingClientRect();
    return {
      left: box.left + (window.pageXOffset - document.documentElement.clientLeft),
      top: box.top + (window.pageYOffset - document.documentElement.clientTop)
    };
  }
docs: Get the offset base on the document.
  @param {Element} element - The target element.
  @returns {Object} The offset data.