JavaScript装饰器_元数据编程实战

{
  "experimentalDecorators": true,
  "emitDecoratorMetadata": true
}

npm install reflect-metadata --save

import 'reflect-metadata';

function Log(target: any, propertyName: string, descriptor: PropertyDescriptor) {
  const originalMethod = descriptor.value;
  descriptor.value = function (...args: any[]) {
    console.log(`Calling "${propertyName}" with arguments:`, args);
    return originalMethod.apply(this, args);
  };

  // 存储元数据
  Reflect.defineMetadata('custom:logged', true, target, propertyName);
}

function Injectable() {
  return function (constructor: Function) {
    Reflect.defineMetadata('di:injectable', true, constructor);
  };
}

function Inject(token: any) {
  return function (target: any, propertyKey: string | symbol, parameterIndex: number) {
    let existingTokens = Reflect.getMetadata('di:tokens', target) || [];
    existingTokens[parameterIndex] = token;
    Reflect.defineMetadata('di:tokens', existingTokens, target);
  };
}

class Container {
  private instances = new Map();

  resolve<T>(token: Function): T {
    if (this.instances.has(token)) {
      return this.instances.get(token);
    }

    const tokens = Reflect.getMetadata('di:tokens', token) || [];
    const dependencies = tokens.map(dep => this.resolve(dep));
    
    const instance = new token(...dependencies);
    this.instances.set(token, instance);
    return instance;
  }
}

@Injectable()
class Logger {
  log(msg: string) { console.log(msg); }
}

@Injectable()
class Service {
  constructor(@Inject(Logger) private logger: Logger) {}

  run() { this.logger.log('Service running'); }
}

"target": "ES2022",
"experimentalDecorators": true,
"emitDecoratorMetadata": true,
"useDefineForClassFields": false