任意值（Any）用来表示允许赋值为任意类型。
let myFavoriteNumber: any = 'seven'; myFavoriteNumber = 7;
变量如果在声明的时候，未指定其类型，那么它会被识别为任意值类型
let something; something = 'seven'; something = 7; something.setName('Tom');
等价于
let something: any; something = 'seven'; something = 7; something.setName('Tom');