Javascript 从对象数组中的对象数组获取对象数组

Question

我有一个注册数组，这个数组里面是一个学生数组。
现在我想要一个只有名字、姓氏和电子邮件的所有学生的数组。

注册数组

[
  0: {
    date: "2019-04-08T13:51:10.215Z"
    onlyVAT: false,
    students: [
      0: {
        email: "ben@test.be",
        firstName: "Bennn",
        lastName: "test",
        phone: "0898989"
        ...
      }
    ]
  }
]

我目前拥有的:

 this.registrations.map(
    registration => registration.students.map(
        student => { return {
          firstName: student.firstName,
          lastName: student.lastName,
          email: student.email
          }}
      )
    );

但这会返回一个数组数组

0: [
  0: {firstName: "Bennn", lastName: "test", email: "ben@test.be"},
  1: ...
]

我想要的是(部分)学生对象的数组

[
  0: {firstName: "Bennn", lastName: "test", email: "ben@test.be"},
  1: ...
]

当然我可以循环并推送到一个新数组，但这不是我想要的

Answer 1

使用flat() 或flatMap()。示例:

  const newArr = registrations.map(
    registration => registration.students.map(
      student => { return {
        firstName: student.firstName,
        lastName: student.lastName,
        email: student.email
      }}
    )
  ).flat();

  console.log(newArr);