Typescript distributed condition type

1. Condition type ( Three mesh operation )

 Judge whether the previous type is the latter type or inherits from the latter type 
 If yes, it returns the first result ,  If not, return the second result 
 grammar : T extends U ? X : Y;

type MyType<T> = T extends string ? string : any;
type res = MyType<boolean>//res = any

2. Distributed condition type

 When the detected type is a union type ,  This condition type is called a distributed condition type 

type MyType<T> = T extends any ? T : never;
//res=string|number|boolean
type res = MyType<string | number | boolean>;

3. from T Weeding can be assigned to U The type of . Exclude

type MyType<T, U> = T extends U ? never : T;
//res=tring | boolean
type res = MyType<string | number | boolean, number>
//res=tring | boolean
type res = Exclude<string | number | boolean, number>

4. extract T Can be assigned to U The type of . Extract

//res = string | number
type res = Extract<string | number | boolean, number | string>

5. from T Middle elimination null and undefined. NonNullable

//res=string | boolean
type res = NonNullable<string | null | boolean | undefined>

6. Get function return value type . ReturnType

//res=number
type res = ReturnType<(()=>number)>

7. Get the tuple type composed of constructor parameters of a class . ConstructorParameters

class Person {
    
    constructor(name:string, age:number){
    }
}
//res = [name:string, age:number]
type res = ConstructorParameters<typeof Person>;

8. Get the tuple type composed of the parameter types of the function . Parameters

function say(name:string, age:number, gender:boolean) {
    
}
//res = [string, age:number, gender:boolean]
type res = Parameters<typeof say>;