// 数组和元素
const arr: (number | string)[] = [1, "2", 3]; //数字或者字符串
const stringArr: string[] = ["a", "b", "c"]; // 字符串
const undefinedArr: undefined[] = [undefined, undefined]; //不能存其他的
//写法1
const objectArr: { name: string; age: number }[] = [
  {
    name: "lll",
    age: 12,
  },
];

// 或者写法2
type User = { name: string; age: number };
const objectArr2: User[] = [
  {
    name: "llll",
    age: 12,
  },
];
// 类型别名
class Teacher {
  name: string;
  age: number;
}
const objectArr3: Teacher[] = [
  new Teacher(),
  {
    name: "www",
    age: 12,
  },
];
//  元祖tuple
const teacherInfo: [string, string, number] = ["ll", "xscs", 15];
// 用处：csv