typescript decorator example

method-decorator-example.ts

// function decorator example

function keepTrack() {
  // stores(or tracks) input and output
  const track: [any, any][] = [];

  return {
    tracker: <MethodDecorator>(
      function(target, prop, descriptor: PropertyDescriptor) {
        const method = descriptor.value;

        descriptor.value = function(...args: any[]) {
          const result = method.apply(this, args);
          track.push([args, result]);
          return result;
        };
      }
    ),
    logger: <() => void>function() {
      return track;
    }
  };
}

const { tracker, logger } = keepTrack();

class Cool {
  @tracker
  static add(a: number, b: number) {
    return a + b;
  }

  @tracker
  static makeString(a: string, b: string, c: string) {
    return `~~~${a + b + c}~~~`;
  }
}

// calls
console.log(Cool.add(5, 8));
console.log(Cool.makeString("lollipop/", "stuffs/", "everywhere"));
console.log("---------------logger-----------------\n", logger());