javascript - 如何将异步代码变成同步代码-nodejs？

Question

这是我的nodejs api代码:

exports.createBusiness = (req, res) => {
  const business = { name: req.body.name };
  Business.create(business)
    .then(() => {
      createSchema() // this function, i pasted below

        .then(() => {
          console.log('6 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>');
        });
    })
    .catch((err) => {
      console.log('err:', err);
    });
};

我的功能:

const createSchema = () => Business.findAll({
  raw: true,
}).then((data) => {
  console.log('1  >>>>>>>>>>>>>>>>>>>>>>>>>>>>');

  data.forEach((client) => {
    console.log('2  >>>>>>>>>>>>>>>>>>>>>>>>>>>>');

    postgresDB.createSchema(client.code).then(() => {
      console.log('3 >>>>>>>>>>>>>>>>>>>>>>>>>>>>');

      Object.keys(postgresDB.models).forEach((currentItem) => {
        console.log('4 >>>>>>>>>>>>>>>>>>>>>>>>>>>>');

        postgresDB.models[currentItem].schema(client.code).sync();
        console.log('5 >>>>>>>>>>>>>>>>>>>>>>>>>>>>');
      });

      console.log('Postgres schema created');
    });
  });
}).catch((err) => {
  console.log('Warning:', err.message);
});

我的输出现在按以下顺序出现在控制台中:

1  
2  
2  
2  
2  
2  
2  
2  
2  
2  
6 



3
4 
5 

我的预期输出在控制台中:(我需要同步执行):

1  
2  
2  
2  
2  
2  
2  
2  
2  
2  

3
4
5

6

如何使用 promise 或回调使其同步运行？

我尝试使用promise.all但不起作用，或者async wait是否很好处理？

Answer 1

只有在所有其他 promise 都得到解决后，您才需要解决由 createSchema 返回的 promise 。将每个客户端映射到一个Promise，然后对其调用Promise.all。您还需要将每个 currentItem 映射到 Promise 并对该 Promise 数组调用 Promise.all。

由于 console.log 的原因，它看起来有点难看:

const createSchema = () => Business.findAll({
  raw: true,
}).then((data) => {
  console.log('1  >>>>>>>>>>>>>>>>>>>>>>>>>>>>');
  const clientPromises = data.map(({ code }) => {
    console.log('2  >>>>>>>>>>>>>>>>>>>>>>>>>>>>');
    return postgresDB.createSchema(code).then(() => {
      console.log('3 >>>>>>>>>>>>>>>>>>>>>>>>>>>>');
      return Promise.all(Object.values(postgresDB.models).map(item => {
        console.log('4 >>>>>>>>>>>>>>>>>>>>>>>>>>>>');
        return item.schema(code).sync()
          .then(() => console.log('5 >>>>>>>>>>>>>>>>>>>>>>>>>>>>'));
      }))
        .then(() => console.log('Postgres schema created'));
    });
  });
  return Promise.all(clientPromises);
}).catch((err) => {
  console.log('Warning:', err.message);
});

没有console.log，它看起来干净多了:

const createSchema = async () => {
  try {
    const data = await Business.findAll({ raw: true });
    const clientPromises = data.map(async ({ code }) => {
      await postgresDB.createSchema(code);
      return Promise.all(Object.values(postgresDB.models).map(item => (
        item.schema(code).sync()
      )));
    });
    return Promise.all(clientPromises);
  } catch (e) {
    console.log('Warning:', e);
  }
};