LeanCloud JS-SDK 遍历表

gistfile1.txt

const forEachAVObject = (query, fn) => {
  let cursor = new Date(0);
  const innerFn = () => {
    return query
    .greaterThan('createdAt', cursor)
    .ascending('createdAt')
    .limit(1000)
    .find()
    .then((objs) => {
      _.forEach(objs, fn);
      if (objs.length === 1000) {
        cursor = _.last(objs).get('createdAt');
        return innerFn();
      }
    });
  };
  return innerFn();
};

// example:
forEachAVObject(new AV.Query('Todo').equalTo('author', 'zhangsan'), (todo) => {
  console.log('>>', todo);
})

大部分这种场景都是要修改对象然后写回数据库的，确保所有操作顺序执行会比较好。

const serialForEach = (objs, fn, done) => {
  let last = objs.pop();
  if (last) {
    fn(last, () => { serialForEach(objs, fn, done); });
  } else {
    done();
  }
}

const forEachAVObject = (query, fn) => {
  let cursor = new Date(0);
  const innerFn = () => {
    return query
    .greaterThan('createdAt', cursor)
    .ascending('createdAt')
    .limit(1000)
    .find()
    .then((objs) => {
      cursor = objs[objs.length-1].get('createdAt');
      serialForEach(objs, fn, innerFn);
    });
  };
  return innerFn();
};

这样就可以做批量修改：

  forEachAVObject(new AV.Query('_User').doesNotExist('status'), (user, done) => {
    user.set('status', 'active');
    user.save().then(done);
  })