获取数组中子项的类型

const array = ['a', 'b', 'c'];
type ArrayType = typeof array;       // string[];
type ItemType = ArrayType[number];  // string
// 简写
type NextItemType = (typeof array)[number];

const array = ['a', '1', true];
type ItemType = (typeof array)[number];       // string | number | boolean
type ItemTypeString = (typeof array)[0];      // string