docs: function setOffset(elem, offset) {
    // set position first, in-case top/left are set even on static elem
    if (css(elem, 'position') === 'static') {
      elem.style.position = 'relative';
    }
  
    var old = getOffset(elem);
    var ret = {};
    var current = undefined;
    var key = undefined;
  
    for (key in offset) {
      if (offset.hasOwnProperty(key)) {
        current = parseFloat(css(elem, key)) || 0;
        ret[key] = current + offset[key] - old[key];
      }
    }
    css(elem, ret);
  }