How to use the hexo-fs.mkdirSync function in hexo-fs

self.load().then(function () {
    if(!fs.existsSync(publicDir)){
      fs.mkdirSync(publicDir);
    }
    if(!fs.existsSync(path.join(publicDir,'assets'))){
      fs.mkdirSync(path.join(publicDir,'assets'));
    }
    self.route.get(doubanLoadingPath)._data().then(function (stream) {
      stream.pipe(fs.createWriteStream(path.join(publicDir, doubanLoadingPath)));
    });
    names.forEach(name => {
      var id = name + "/index.html";
      self.route.get(id) && self.route.get(id)._data().then(function (contents) {
        fs.writeFile(path.join(publicDir, id), contents);
        log.info("Generated: %s", id);
      });
    });
  });
});

mkdir(dir) {
    if (!fs.existsSync(dir)){
      fs.mkdirSync(dir);
    }
  }

self.load().then(function () {
    if(!fs.existsSync(publicDir)){
      fs.mkdirSync(publicDir);
    }
    if(!fs.existsSync(path.join(publicDir,'assets'))){
      fs.mkdirSync(path.join(publicDir,'assets'));
    }
    self.route.get(doubanLoadingPath)._data().then(function (stream) {
      stream.pipe(fs.createWriteStream(path.join(publicDir, doubanLoadingPath)));
    });
    names.forEach(name => {
      var id = name + "/index.html";
      self.route.get(id) && self.route.get(id)._data().then(function (contents) {
        fs.writeFile(path.join(publicDir, id), contents);
        log.info("Generated: %s", id);
      });
    });
  });
});