lwt09

let str = 'a aa a a ' str.split(' ').join('') str.replace(/\s*/g,'')

``` type User = { id: number; kind: string; }; function makeCustomer(u: T): T { // Error（TS 编译器版本：v4.4.2） // Type '{ id: number; kind: string; }' is not assignable to...

``` function f(a: number, b: number): number; function f(a: string, b: string): string; function f(a: number | string, b: number | string) { if (typeof a === "string") { return...