docs: function setLeftTop(elem, offset, option) {
    // set position first, in-case top/left are set even on static elem
    if (css(elem, 'position') === 'static') {
      elem.style.position = 'relative';
    }
    var presetH = -999;
    var presetV = -999;
    var horizontalProperty = getOffsetDirection('left', option);
    var verticalProperty = getOffsetDirection('top', option);
    var oppositeHorizontalProperty = oppositeOffsetDirection(horizontalProperty);
    var oppositeVerticalProperty = oppositeOffsetDirection(verticalProperty);
  
    if (horizontalProperty !== 'left') {
      presetH = 999;
    }
  
    if (verticalProperty !== 'top') {
      presetV = 999;
    }
    var originalTransition = '';
    var originalOffset = getOffset(elem);
    if ('left' in offset || 'top' in offset) {
      originalTransition = Object(__WEBPACK_IMPORTED_MODULE_0__propertyUtils__["c" /* getTransitionProperty */])(elem) || '';
      Object(__WEBPACK_IMPORTED_MODULE_0__propertyUtils__["e" /* setTransitionProperty */])(elem, 'none');
    }
    if ('left' in offset) {
      elem.style[oppositeHorizontalProperty] = '';
      elem.style[horizontalProperty] = presetH + 'px';
    }
    if ('top' in offset) {
      elem.style[oppositeVerticalProperty] = '';
      elem.style[verticalProperty] = presetV + 'px';
    }
    // force relayout
    forceRelayout(elem);
    var old = getOffset(elem);
    var originalStyle = {};
    for (var key in offset) {
      if (offset.hasOwnProperty(key)) {
        var dir = getOffsetDirection(key, option);
        var preset = key === 'left' ? presetH : presetV;
        var off = originalOffset[key] - old[key];
        if (dir === key) {
          originalStyle[dir] = preset + off;
        } else {
          originalStyle[dir] = preset - off;
        }
      }
    }
    css(elem, originalStyle);
    // force relayout
    forceRelayout(elem);
    if ('left' in offset || 'top' in offset) {
      Object(__WEBPACK_IMPORTED_MODULE_0__propertyUtils__["e" /* setTransitionProperty */])(elem, originalTransition);
    }
    var ret = {};
    for (var _key in offset) {
      if (offset.hasOwnProperty(_key)) {
        var _dir = getOffsetDirection(_key, option);
        var _off = offset[_key] - originalOffset[_key];
        if (_key === _dir) {
          ret[_dir] = originalStyle[_dir] + _off;
        } else {
          ret[_dir] = originalStyle[_dir] - _off;
        }
      }
    }
    css(elem, ret);
  }