How to use the raphael.getTotalLength function in raphael

function preprocessStrokes(data, options) {
  const strokes = [];
  let stroke;
  let length;

  for (let i = 0; i < data.length; i += 1) {
    for (let j = 0; j < data[i].length; j += 1) {
      length = Raphael.getTotalLength(data[i][j].path);
      stroke = {
        char: i,
        length,
        duration: length * options.step * 1000,
        path: data[i][j].path,
        groups: data[i][j].groups,
        text: data[i][j].text,
        object: {
          path: null,
          text: null,
        },
      };
      strokes.push(stroke);
    }
  }