docs: function getTotalLength(el) {
    if (el.getTotalLength) return el.getTotalLength();
    switch(el.tagName.toLowerCase()) {
      case 'circle': return getCircleLength(el);
      case 'rect': return getRectLength(el);
      case 'line': return getLineLength(el);
      case 'polyline': return getPolylineLength(el);
      case 'polygon': return getPolygonLength(el);
    }
  }