javascript - 我们如何减少嵌套数组？

Question

我将学生 ID 与标记映射的对象如下:

[
    {id: 111, marks: [{sub: 'eng', mark: 90}, {sub: 'maths', mark: 20}]},
    {id: 222},
    {id: 333, marks: []},
    {id: 444, marks: [{sub: 'eng', mark: 70}]}
]

我想减少它如下:

{
    marks[0]: "0:eng:90", // studentIndex:subject_name:mark
    marks[1]: "0:maths:20",
    marks[2]: "3:eng:70"
}

在上面的结果中，键是“marks[]”，值是一个字符串，它是studentIndex、主题和标记的串联。 所以这里 0:eng:90 表示索引为 0 的学生在英语科目中获得了 90 分

我正在使用 lodash 并尝试了以下方法:

reduce(studentList, (acc, student, studentIndex) => {
    map(get(student, 'marks'), (marks) => {
      acc[`marks[${keys(acc).length}]`] = `${studentIndex}:${marks.sub}:${marks.mark}`;
    });
    return acc;
  }, {});

还有其他更好的方法吗？

Answer 1

没有 Lodash

var studentList = [{"id":111,"marks":[{"sub":"eng","mark":90},{"sub":"maths","mark":20}]},{"id":222},{"id":333,"marks":[]},{"id":444,"marks":[{"sub":"eng","mark":70}]}]

var result = studentList.reduce((acc, student, studentIndex) => {
  (student.marks || []).map((marks) => {
    acc[`marks[${Object.keys(acc).length}]`] = `${studentIndex}:${marks.sub}:${marks.mark}`;
  });
  return acc;
}, {});

console.log(result)

使用 Lodash

var studentList = [{"id":111,"marks":[{"sub":"eng","mark":90},{"sub":"maths","mark":20}]},{"id":222},{"id":333,"marks":[]},{"id":444,"marks":[{"sub":"eng","mark":70}]}]

var result = _.reduce(studentList, (acc, student, studentIndex) => {
  _.map(student.marks || [], (marks) => {
    acc[`marks[${_.keys(acc).length}]`] = `${studentIndex}:${marks.sub}:${marks.mark}`;
  });
  return acc;
}, {});

console.log(result)

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