Angular2 multiple constructor implementations are not allowed TS2392

Making multiple constructors with the same parameters doesn't make sense unless they have different types, in Typescript you can do the following:

class Foo {
  questions: any[];
  constructor(service: QuestionSignupStepOneService, param2?: Param2Type) { 

    this.questions = service.getQuestions(); 
    if(param2){
        console.log(param2);
    }
  }
}

This is equal to two constructors, the first one is new Foo(service) and the second one is new Foo(service, param2).

Use ? to state that the parameter is optional.

If you want two constructors with the same parameter but for different types you can use this:

class Foo {
  questions: any[];
  constructor(service: QuestionSignupStepOneService | QuestionSignupStepOneAService) {

    if(service instanceof QuestionSignupStepOneService){
       this.questions = service.getQuestions(); 
    }
    else {
       this.questions = service.getDifferentQuestions(); 
    }
  }
}