【Q693】在 ts 中如何实现 Partial

[shfshanyue]

实现 Partial，使得 Object 所有的属性变为可选属性。

PS: Partial 已经在 TS 中原生实现，见文档: https://www.typescriptlang.org/docs/handbook/utility-types.html#partialtype

type User = {
  id: number;
  age: number;
  name: string;
}

// Output:
// type PartialUser = {
//   id?: number | undefined;
//   age?: number | undefined;
//   name?: string | undefined;
// }
type PartialUser = Partial<User>

以下是使用案例

interface Todo {
  title: string;
  description: string;
}

function updateTodo(todo: Todo, fieldsToUpdate: Partial<Todo>) {
  return { ...todo, ...fieldsToUpdate };
}

const todo1 = {
  title: "organize desk",
  description: "clear clutter",
};

const todo2 = updateTodo(todo1, {
  description: "throw out trash",
});

[shfshanyue]

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