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enum MyEnum { A, B, C };

如果我想要另一种类型，即该枚举的键的联合字符串，我可以执行以下操作:

type MyEnumKeysAsStrings = keyof typeof MyEnum;  // "A" | "B" | "C"

type Person = { age: number; name: string; alive: boolean };
 
type I2 = Person[keyof Person];
//type I2 = string | number | boolean

const RestfulMethod = {
  get: 'GET',
  post: 'POST',
  put: 'PUT',
  delete: 'DELETE'
} as const


type IRestfulMethod = typeof RestfulMethod
type TypeRestfulMethod = IRestfulMethod[keyof IRestfulMethod]
// type TypeRestfulMethod = 'GET' | 'POST' | 'PUT' | 'DELETE'

type Person = { age: number; name: string; alive: boolean };
 
type I2 = keyof Person
//type I2 = 'age' | 'name' | 'alive'

let obj = {
  name: 'hello',
  age: 18, 
  eat () {
    return 'food'
  },
  link () {
    return 'dog'
  }
}

type methodsPick<T> = {[K in keyof T]: T[K] extends Function ? K : never}[keyof T];
// T1 = 'eat' | 'link'
type T1 = methodsPick<typeof obj>

Partial<Type>

pick

通过从 Type 中选择一组属性 Keys（字符串文字或字符串文字的联合）来构造一个类型。

interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
 
type TodoPreview = Pick<Todo, "title" | "completed">;
 
const todo: TodoPreview = {
  title: "Clean room",
  completed: false,
};

todo;
 
const todo: TodoPreview

omit

与pick相反，通过从 Type 中选择所有属性然后删除 Keys（字符串文字或字符串文字的联合）来构造一个类型。

interface Todo {
  title: string;
  description: string;
  completed: boolean;
  createdAt: number;
}
 
type TodoPreview = Omit<Todo, "description">;
 
const todo: TodoPreview = {
  title: "Clean room",
  completed: false,
  createdAt: 1615544252770,
};