变量定义函数类型

let addFunc: (x: number, y: number) => number;

接口定义函数类型

interface AddFunc1 {(x: number, y: number): number;
}

类型别名定义函数类型

type AddFunc2 = (x: number, y: number) => number;

实现具体函数

let add1: AddFunc1 = (x, y) => x + y;
let add2: AddFunc2 = (x, y) => x + y;

混合接口定义类库

interface Lib {(): void;version: string;doSomething(): void;
}function getLib() {let lib: Lib = (() => {}) as Lib;lib.version = '1.0.0';lib.doSomething = () => {}return lib;
}let lib1 = getLib();
lib1();
lib1.version;
lib1.doSomething();