属性修饰器和参数修饰器

示例代码：

const PropertyDecorator: PropertyDecorator = (
        target: Object,
        propertyKey: string | symbol
    ) => {
        // 测试参数
        //  console.log(target)
        //  console.log(propertyKey)
    };
    const ParamsDecorator: ParameterDecorator = (
        target: Object,
        propertyKey: string | symbol,
        parameterIndex: number
    ) => {
        console.log(parameterIndex);
    };
    // 属性装饰器和参数装饰器
    class Player {
        // 创建一个属性
        // 使用一个属性装饰器
        @PropertyDecorator
        public username: string = 'admin';
        //参数修饰器
        public run(idx: number, @ParamsDecorator keywords: string): void {
            console.log('run方法正在被执行');
            // console.log(this.username)
        }
    }
    new Player().run(100, '小明');

通过属性属性符来劫持属性，并且将属性值都改为小写：

// 属性修饰符
  let value: string = 'hello,world';
    const propertyDecorator: PropertyDecorator = (
        target: object,
        propertyName: string | symbol,
    ) => {

        Object.defineProperty(target, propertyName, {
            get() {
        return value.toLowerCase();
      },
      set(v) {
        value = v;
      }
        });
    };
    class Player {
    @propertyDecorator
        public username: string | undefined;
    }

  const p = new  Player();
  console.log(p.username);
  p.username = 'ABC';
  console.log(p.username);