code: function getFilePath(sourcePath, filename, subDir) {
      if (subDir === void 0) { subDir = ''; }
      var filePath = filename
          .replace(path.resolve(sourcePath), '')
          .replace(path.basename(filename), '');
      if (subDir) {
          filePath = filePath.replace(subDir + path.sep, '');
      }
      if (/^[\/\\]/.test(filePath)) {
          filePath = filePath.substr(1);
      }
      return filePath.replace(/\\/g, '/');
  }
docs: get file path by filename