Typescript generic type left side vs right side of function-CodePudding

I'm trying to learn typescript generics, but couldn't understand the difference between these two types:

type A<T> = (x: T) => T;
type B = <T>(x: T) => T;

I only found one video on yt, but unfortunately this wasn't enough to make my brain understand...

Does any1 have a simple explanation? Thanks!

CodePudding user response：

With type A<T> = (x: T) => T; the generic has to be passed when using the type, for example:

// here a is (c: string) => string;
let a: A<string> = x => x;

// a only accept string
a('foo')

With type B = <T>(x: T) => T; the generic is passed when the function is called:

// no generic yet
let b: B = x => x;

// here b is (x: number) => number;
b<number>(42);

// here b is (x: boolean) => boolean;
b<boolean>(true);

// you can omit the generic since TS will infer it
// here b is (x: string) => string;
b('hello')