Typescript 类型2019-09-12Θ

type Foo = {
    a: number;
    b: string;
    c: boolean;
};
type FooPartial = Partial<Foo>;
//=> { a?: number; b?: string; c?: boolean }

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

type WithOptional<T, K extends keyof T> = Omit<T, K> & Partial<Pick<T, K>>;

type AccountFormType = {
  name: string,
  endpoint: string,
  accessKey: string,
  secretKey: string,
  region?: string,
}
type AccountFormOptionalType = WithOptional<AccountFormType, 'name' | 'endpoint'>
// => 
// {
//   name?: string;
//   accessKey?: string
//   secretKey: string
//   endpoint: string
//   region?: string
// }

type Foo = {
    a: number;
    b: string;
    c: boolean;
};
type FooWithAC = Pick<Foo, 'a' | 'c'>;
//=> { a: number; c: boolean };

type Pick<T, K extends keyof T> = {
  [P in K]: T[P];
};

type Foo = {
    a: number;
    b: string;
    c: boolean;
};
type FooWithoutA = Omit<Foo, 'a' | 'c'>;
//=> { b: string };

type Except<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>

type Foo = {
    a: number;
    b: string;
    c: boolean;
};
type FooRecordWithString = Record<string, Foo>
//=> { [x: string]: Fo }

type Record<K extends keyof any, T> = {
    [P in K]: T;
}

type Foo = {
    a: number;
    b: string;
    c: boolean;
};
type FooKey = keyof Foo; //=> "a" | "b" | "c"
type FooKeyWithoutAC = Exclude<KeyOf, 'a' | 'c'> //=> "b"

type Exclude<T, U> = T extends U ? never : T;

type Foo = {
    a: number;
    b: string;
    c: boolean;
};
type FooKey = keyof Foo; //=> "a" | "b" | "c"
type FooKeyWithAC = Extract<KeyOf, 'a' | 'c'> //=> "a" | "c"

type Extract<T, U> = T extends U ? T ： never;