作用

Partial<T> 可以快速把某个接口类型中定义的属性变成可选的(Optional)

DEMO

interface People {
  age: number;
  name: string;
}

const Jerry:People = {
    age: 10,
    name: 'Jerry'
};

type AnonymousPeople = Partial<People>;

const tom:AnonymousPeople = {
    name: 'Tom'
};

源码

type Partial<T> = {
    [P in keyof T]?: T[P];
};

in keyof

Keyof 用于提取类型的key,返回keys的类型数组