Tiny jQuery tool to pin absolute-positioned div in current screen position and unpin it back

pin.js

;(function() {

  var FIXED = 'fixed';
  var ABSOLUTE = 'absolute';
  var $w = $(window);

  window.pin = function(obj) {
    var objPos = obj.css('position');
    if (objPos == FIXED) return;
    var objOffset = obj.offset();
    var objPos = obj.position();
    var scrollTop = $w.scrollTop();
    var scrollLeft = $w.scrollLeft();
    obj.attr({
      posX: objPos.left - scrollLeft,
      posY: objPos.top - scrollTop
    }).css({
      position: FIXED,
      left: objOffset.left - scrollLeft,
      top: objOffset.top - scrollTop
    });
  }

  window.unpin = function(obj) {
    var objPos = obj.css('position');
    if (objPos == ABSOLUTE) return;
    var objOffset = obj.offset();
    var objPos = obj.position();
    var originalPosX = obj.attr('posX')|0;
    var originalPosY = obj.attr('posY')|0;
    obj.css({
      position: ABSOLUTE,
      left: objOffset.left - objPos.left + originalPosX,
      top: objOffset.top - objPos.top + originalPosY
    });
  }

})(window);