TypeScript 获取函数的参数类型、返回值类型及定义返回函数类型

function test(lzwme: string, idx: number) {
  return {
    lzwme,
    idx,
  };
}

type TestArgsType = Parameters<typeof test>;
// TestArgsType => [lzwme: string, idx: number]

type TestArgsType = Parameters<typeof test>[1];
// TestArgsType => idx: number

type Parameters<T extends (...args: any) => any> = T extends (...args: infer P) => any ? P : never;

type TestReturnType = ReturnType<typeof test>;

type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;

//第一种形式
let c: Function;
c = function(): void {
console.log('It work');
}

//第二种形式
function test(): Function{
return function():void{
console.log('it work');
}
}

let a:Function = test();
a();

//第三种形式，箭头函数
let d: (para: string) => string;
d = function(param: string): string {
return param;
}

//第四种形式，类型别名，箭头函数
type e = (para: string) => string;
const f:e = function(pass: string): string{

return pass;

}

//第五种形式，接口
interface g{
(para: string): string;
}
const h: g = function(pass: string): string{
return pass;
}

let myAdd: (x:number, y:number) => number =
function(x: number, y: number): number { return x + y; };

let x: number = 10;

let myAdd: (aaaaaaaaaaaaaaaaaaaaaa:number, bbbbbbbbbbbbbbbbbbbbbbbb:number) => number =
function(x: number, y: number): number { return x + y; };

let x = 10;

const myAdd = (x: number, y: number) => x + y;