exp-decorator.ts

  function option(name: string): Function;
  function option(target: any, propertyName: string, propertyDescriptor?: PropertyDescriptor): void;
  function option(...args: any[]): Function|void {

    if (args.length >= 2) {
      _option(args[0], args[1], args[2]);
      return;
    } else {
      console.log("evaluated", args);
      return (...args2: any[]) => {
        _option(args2[0], args2[1], args2[2], args[0]);
      };
    }
  }
  function _option(target: any, propertyName: string, propertyDescriptor?: PropertyDescriptor, hoge?: any) {
    console.log("called", target, propertyName, propertyDescriptor, hoge);
    const type = Reflect.getMetadata("design:type", target, propertyName);
    switch (type) {
      case String:
        console.log("String");
        break;
      case Object:
        console.log("Object", type);
        break;
      case Number:
        console.log("Number");
        break;
      case Boolean:
        console.log("Boolean");
        break;
      case Date:
        console.log("Date");
        break;
      case Function:
        console.log("Function", type);
        break;
      default:
        console.log("other", type);
    }
  }

  console.log("----------------------------------------")
  console.log("Target1")

/*
evaluated [ 'a' ]
evaluated [ 'b' ]
called Target1 {} year undefined b
Number
called Target1 {} year undefined a
Number
called Target1 {} year undefined undefined
Number
*/

  class Target1 {
    @option
    @option("a")
    @option("b")
    public year: number;
  }

  console.log("----------------------------------------")
  console.log("Target2")

/*
Target2
called Target2 {} name undefined undefined
String
called Target2 {} age undefined undefined
Number
called Target2 {} created undefined undefined
Date
called Target2 {} admin undefined undefined
Boolean
called Target2 {} year { get: [Function: get year],
  set: undefined,
  enumerable: false,
  configurable: true } undefined
Object function Object() { [native code] }
called Target2 {} run { value: [Function: run],
  writable: true,
  enumerable: false,
  configurable: true } undefined
Function function Function() { [native code] }
*/

  class Target2 {
    @option
    private name: string;
    @option
    private age: number;
    @option
    private created: Date;
    @option
    private admin: boolean;
    @option
    public get year() {
      return 2018;
    }
    @option
    public run() {

    }
  }


  console.log("----------------------------------------")
  console.log("Target3")

/*
Target3
called Target3 {} age undefined undefined
Object function Object() { [native code] }
*/

  class Target3 {
    @option
    private age: (string | number);
  }