Question

我写了一个控制器，但我不明白为什么在该方法中为什么我的数组正确，所以我需要发送它，对于.then（），我的数组为空。我无法在循环的中间发送结果。

exports.getRecipientdata = (req, res) => {
  const userId = req.params.recipientId;
  const sendersArray = [];
  Transaction.findAll({
    where: {
      id_recipient: userId,
    },
  }).then(transactions => {
    for (let i = 0; i < transactions.length; i++) {
      User.findOne({
        where: {
          id: transactions[i].id_sender,
        },
        attributes: ['id', 'name', 'surname'],
        include: [
          {
            model: Transaction,
            where: { id_sender: db.Sequelize.col('user.id') },
            attributes: [
              'amount_money',
              'date_time',
              'transfer_title',
              'id_recipient',
              'id_sender',
            ],
          },
        ],
      })
        .then(sender => {
          sendersArray.push(sender);
          console.log(JSON.stringify(sendersArray)); // ok
        })
        .catch(err => {
          console.log(err);
        });
    }
    console.log('sendersArray', sendersArray); // empty?
    res.send(sendersArray);
  });
};

Answer 1

for循环正在发出异步填充sendersArray的请求。如果您在console.log(sendersArray)循环运行之后for同步地，则说明该循环尚未被填充。使用for和.map来等待所有请求完成，而不是Promise.all循环：

exports.getRecipientdata = (req, res) => {
  const userId = req.params.recipientId;
  const sendersArray = [];
  Transaction.findAll({
    where: {
      id_recipient: userId,
    },
  }).then(transactions => {
    return Promise.all(transactions.map(({ id_sender }) => (
      User.findOne({
        where: {
          id: id_sender,
        },
        attributes: ['id', 'name', 'surname'],
        include: [
          {
            model: Transaction,
            where: { id_sender: db.Sequelize.col('user.id') },
            attributes: [
              'amount_money',
              'date_time',
              'transfer_title',
              'id_recipient',
              'id_sender',
            ],
          },
        ],
      })
        .then(sender => {
          sendersArray.push(sender);
        })
        .catch(err => {
          console.log(err);
        })
    )));
  })
  .then(() => {
    res.send(sendersArray);
  });
};

另一种可能性是使用push创建的数组，而不是Promise.all来创建外部变量，并使用布尔值过滤以删除假值（因为catch缺少返回值将导致undefined数组的结果中出现Promise.all个变量）：

exports.getRecipientdata = (req, res) => {
  const userId = req.params.recipientId;
  Transaction.findAll({
    where: {
      id_recipient: userId,
    },
  }).then(transactions => {
    return Promise.all(transactions.map(({ id_sender }) => (
      User.findOne({
        where: {
          id: id_sender,
        },
        attributes: ['id', 'name', 'surname'],
        include: [
          {
            model: Transaction,
            where: { id_sender: db.Sequelize.col('user.id') },
            attributes: [
              'amount_money',
              'date_time',
              'transfer_title',
              'id_recipient',
              'id_sender',
            ],
          },
        ],
      })
        .catch(err => {
          console.log(err);
        })
    )));
  })
  .then((sendersArray) => {
    res.send(sendersArray.filter(Boolean));
  });
};

为什么我的数组在.then（）之后为空？的JavaScript

1 个答案: