type ClassMethodDecorator = (value: Function,context: {kind: 'method';name: string | symbol;static: boolean;private: boolean;access: { get: () => unknown };addInitializer(initializer: () => void): void;}
) => Function | void;

1、如果装饰器返回一个函数就会替代装饰的函数

function replaceMethod(originMethod: Function,content: ClassMethodDecoratorContext
) {return function (...args) {console.log(args);originMethod.call(this, args);};
}

2、装饰器可以传参数

@replaceMethod('7777')
myMethodfunction replaceMethod(...args) {return function (originMethod: Function,content: ClassMethodDecoratorContext) {return function (...hello) {originMethod.call(this,hello);};};
}

装饰器接参数重新类中的方法 停留时间执行
function Greeter(value: any, context: any) {}function replaceMethod(num: number) {return function (originMethod: Function,content: ClassMethodDecoratorContext) {return function (...hello) {setTimeout(() => {originMethod.call(this, hello);}, num);};};
}@Greeter
class User {[propertyName: string]: any;name: string;constructor(name: string) {this.name = name;}@replaceMethod(1000)hello(u) {console.log("元旦快乐" + " " + this.name + u);}
}let u = new User("zhansan");
u.hello("0999");

3、方法装饰器的 { addInitializer } 相当于constructor 初始化对象 参数是一个函数，可以访问当前this

function initialInstance(originMethod: Function,content: ClassMethodDecoratorContext
) {content.addInitializer(function () {this[content.name] = this[content.name].bind(this);});
}
class Person {name: string;constructor(name: string) {this.name = name;// greet() 绑定 this// this.greet = this.greet.bind(this);}@initialInstancegreet() {console.log(`Hello, my name is ${this.name}.`);}
}

4、一个方法可以有多个装饰器

/**** @param originMethod @type {Function}* @param content  @type {ClassMethodDecoratorContext}*/
function collectMethods(originMethod: Function,{ addInitializer, name }: ClassMethodDecoratorContext
) {addInitializer(function () {let _this = this as Person;if (!_this.collectMethodSet) {_this.collectMethodSet = new Set();}_this.collectMethodSet.add(name);});
}
function initialInstance(originMethod: Function,content: ClassMethodDecoratorContext
) {content.addInitializer(function () {this[content.name] = this[content.name].bind(this);});
}
class Person {name: string;constructor(name: string) {this.name = name;}[p: string]: any;@initialInstance@collectMethodsgreet() {console.log(`Hello, my name is ${this.name}.`);}@collectMethodshandle() {}
}const g = new Person("张三");
g.greet() //Hello, my name is 张三
console.log(g.collectMethodSet); //Set(2) { 'greet', 'handle' }