//提取T中不包含在U中的类型
type Exclude<T, U> = T extends U ? never : T;
type T = Exclude<"a" | "b" | "c", "a" | "b">;
 
("a" extends "a" | "b" ? never : "a") // => never
| ("b" extends "a" | "b" ? never : "b") // => never
| ("c" extends "a" | "b" ? never : "c") // => "c"
 
never | never | "c" // => "c"

type Partial<T> = { [P in keyof T]?: T[P] };
type Required<T> = { [P in keyof T]-?: T[P] };
 
// From T, pick a set of properties whose keys are in the union K
type Pick<T, K extends keyof T> = { [P in K]: T[P] };
 
type Readonly<T> = { readonly [P in keyof T]: T[P] };
 
type Item = { a: string; b: number; c: boolean };
type T1 = Partial<Item>; // {a?: string | undefined; b?: number | undefined; c?: boolean | undefined;}

// Construct a type with a set of properties K of type T
type Record<K extends keyof any, T> = {
    [P in K]: T;
};
//例子：搭配联合类型
type RequestMethods = 'GET'|'POST'| 'DELETE'
type MethodsAny = Record<RequestMethods, string>
let method1:MethodsAny = {
    GET: '200',
    POST: '300',
    DELETE:'400'
}
//例子：搭配接口
interface PersonModel {
    name:string,
    age:number
}
type student = Record<string, PersonModel>
 
let s:student = {
    'student1':{
        name:'小凌',
        age:18
    },
    'student2':{
        name:'小李',
        age:19
    }
}

//提取T中包含在U中的类型
type Extract<T, U> = T extends U ? T : never;
type NonNullable<T> = T extends null | undefined ? never : T;
type Parameters<T extends (...args: any) => any> = T extends (...args: infer P) => any ? P : never;
//返回函数的返回类型
type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;