javascript - array.push 没有根据序列推送对象，而某些对象使用等待执行操作

Question

我正在尝试使用map循环我的对象，在map内部我需要使用sequelize执行操作，因此我使用async和Promise.all来支持async，但它给我的结果是对象序列与原始序列不同，该序列以不使用sequelize执行操作的数据开始。

例如:

const data = await Student.findAll({
    limit: 2,
    where: {
        level: 'Primary 1'
    },
    order: [['id', 'ASC']]
}).then(async resultStudent => {
    // [{"id": 1, "name": "Alex", "gender": "Male", "level": "Primary 1"}, {"id": 2, "name": "Betty", "gender": "Female", "level": "Primary 1"}]

    let finalData = [];

        await Promise.all(
            resultStudent.map(async (e, index) => {

                let studentHobbies;
                if(e.gender == 'Male'){
                    studentHobbies = await Hobbies.findOne({
                        where: {
                            studentID: e.id
                        }
                    })
                }

                let obj = {
                    id: e.id,
                    hobby: studentHobbies ? studentHobbies.hobbyName : null
                };

                finalData.push(obj);
            })
        )
})

上面的代码给出的结果为:

[{
    "id": 2,
    "hobby": null
}, {
    "id": 1,
    "hobby": "Playing Guitar, and Basketball"
}]

虽然我的预期结果是:

[{
    "id": 1,
    "hobby": "Playing Guitar, and Basketball"
}, {
    "id": 2,
    "hobby": null
}]

Answer 1

尝试使用带有异步回调的 map 来保持顺序:

const data = await Student.findAll({
    limit: 2,
    where: {
        level: 'Primary 1'
    },
    order: [['id', 'ASC']]
}).then(resultStudent => Promise.all(
    resultStudent.map(async student => ({
        id: student.id,
        hobby: (student.gender === 'Male')
          ? await Hobbies.findOne({ where: { studentID: student.id } })
          : null
    })
)))

编辑:更易于阅读的版本

const data = await Student.findAll({ // array of ordered results from query
    limit: 2,
    where: {
        level: 'Primary 1'
    },
    order: [['id', 'ASC']]
}).then(results =>
    results.map(async ({ id, gender }) => ({ // array of promises that run asynchronously and resolve with formatted objects
        id,
        hobby: (gender === 'Male')
          ? await Hobbies.findOne({ where: { studentID: id } })
          : null
    }))
  ).then(Promise.all) // array of results of resolved promises, in same order. resolves when all have completed

这三个数组中的每一个都包含在一个 promise 中。 const data = wait 从 Promise 链的末尾提取最终结果。