TypeScript里的工具类型Partial的用法

在SAP Spartacus的源代码里我们可以观察到很多Partial的使用场景：

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

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

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

const Tom: People = {
	name: 'Tom'
}

上述代码会发生编译时错误：

1.ts:11:7 - error TS2741: Property ‘age’ is missing in type ‘{ name: string; }’ but required in type ‘People’.

解决方法：

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

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

type AnonymousPeople = Partial<People>;

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

编译之后：

var Jerry = {
    age: 10,
    name: 'Jerry'
};
var tom = {
    name: 'Tom'
};

这个工具类型的实现毫无神奇之处：

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

我们完全可以自行实现：

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

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

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

type AnonymousPeople = JerryPartial<People>;

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

更多Jerry的原创文章，尽在：“汪子熙”: