.map 函数中的异步验证

Question

我正在使用 Node JS、Sequelize 和 Postgres 数据库开发应用程序的后端。注册课程时，用户必须告知哪些组织、公司和教师将与其相关联。组织 ID 通过数组传递到后端，我正在尝试进行检查以确保传递的 ID 存在。到目前为止我所做的是：const { organizations } = req.body;const organizationsArray = organizations.map(async (organization) => {  const organizationExists = await Organization.findByPk(organization);  if (!organizationExists) {    return res      .status(400)      .json({ error: `Organization ${organization} does not exists!` });  }  return {    course_id: id,    organization_id: organization,  };});await CoursesOrganizations.bulkCreate(organizationsArray);

Answer 1

正在Array.map()返回一个承诺数组，您可以使用Promise.all(). 在地图内部，您应该使用throw new Error()break out of map - 将引发此错误Promise.all()，然后您可以捕获它并将错误返回给客户端（或吞下它等）。

这是您的模式的更正版本，解决了 Promise 结果。

const { organizations } = req.body;

try {

  // use Promise.all to resolve the promises returned by the async callback function

  const organizationsArray = await Promise.all(

    // this will return an array of promises

    organizations.map(async (organization) => {

      const organizationExists = await Organization.findByPk(organization, { 

        attributes: ['id'], // we only need the ID

        raw: true, // don't need Instances

      });

      if (!organizationExists) {

        // don't send response inside the map, throw an Error to break out

        throw new Error(`Organization ${organization} does not exists!`);

      }

      // it does exist so return/resolve the value for the promise

      return {

        course_id: id,

        organization_id: organization,

      };

    })

  );

  // if we get here there were no errors, create the records

  await CoursesOrganizations.bulkCreate(organizationsArray);

  // return a success to the client

  return res.json({ success: true });

} catch (err) {

  // there was an error, return it to the client

  return res.status(400).json({ error: err.message }); 

}

Organizations这是一个重构版本，通过在一个查询中获取所有内容然后进行检查/创建插入，速度会更快一些Course。

const { Op } = Sequelize;

const { organizations } = req.body;

try {

  // get all Organization matches for the IDs

  const organizationsArray = await Organization.findAll({

    attributes: ['id'], // we only need the ID

    where: {

      id: {

        [Op.in]: organizations, // WHERE id IN (organizations) 

      }

    },

    raw: true, // no need to create Instances

  });

  // create an array of the IDs we found

  const foundIds = organizationsArray.map((org) => org.id);

  // check to see if any of the IDs are missing from the results

  if (foundIds.length !== organizations.length) {

    // Use Array.reduce() to figure out which IDs are missing from the results

    const missingIds = organizations.reduce((missingIds, orgId) => {

      if (!foundIds.includes(orgId)){

        missingIds.push(orgId);

      }

      return missingIds;

    }, []); // initialized to empty array

    throw new Error(`Unable to find Organization for: ${missingIds.join(', ')}`);

  }

  // now create an array of courses to create using the foundIds

  const courses = foundIds.map((orgId) => {

    return {

      course_id: id,

      organization_id: orgId,

    }; 

  });

  // if we get here there were no errors, create the records

  await CoursesOrganizations.bulkCreate(courses);

  // return a success to the client

  return res.json({ success: true });

} catch (err) {

  // there was an error, return it to the client

  return res.status(400).json({ error: err.message }); 

}

Answer 2

如果你有一个 ID 数组并且你想检查它们是否存在你应该使用 (in) 运算符，这使得你只访问数据库一次并一次获取所有记录（而不是获取它们一个一个循环），在你得到这些记录后，你可以检查它们的长度以确定它们是否都存在。

const { Op } = require("sequelize");

let foundOrgs = await Organization.findAll({

  where: {

    id: {

      [Op.in]: organizationsArray,

    }

  }

});