overscroll/es/utils/dom/getOffset.js

scroll

export var getOffset = function getOffset(_ref) {
  var win = _ref.win,
      body = _ref.body,
      html = _ref.html;
  return function (node) {
    var box = node.getBoundingClientRect();

    // < ie8 不支持 win.pageXOffset, 则使用 html.scrollLeft
    return {
      left: box.left + (win.pageXOffset || html.scrollLeft) - (html.clientLeft || body.clientLeft || 0),
      top: box.top + (win.pageYOffset || html.scrollTop) - (html.clientTop || body.clientTop || 0)
    };
  };
};

export var getPosition = function getPosition(scope) {
  return function (node) {
    // if ( node.parentNode === scope.body ) {
    //   return getOffset( scope )( node );
    // }

    var parent = node.parentNode;
    var parentOffset = getOffset(scope)(parent);
    var offset = getOffset(scope)(node);

    return {
      left: offset.left - parentOffset.left,
      top: offset.top - parentOffset.top
    };
  };
};