Use of .map with http in Angular 2

Question

I want to know that do we really need .map when calling any api using http in Angular 2 ?

Please check my below code. It is working fine with .map and even without .map . If api returns data then it will return success else it will return error. I will also return any model data from here after performing some action. So, do I need Observable ? Is there any benefit of using it ? I am using .subscribe at component side to receive data. Is this fine or do I need any improvement ?

returnData: ReturnData;
callyAPI(body: modelData) {
     return this.http.post(URL, body)
           .do(data => {
                for (let i = 0; i < data.length; ++i) {
                   this.returnData.push(data[i]);
                }
                return this.returnData;
            },
               error => {});
      });
}

Answer 1

You don't need to use map but do is definitly the wrong operator here

do is supposed to execute some code for every event, but not to modify the events value, while map can update or replace the event by a different value like you do in your example.

https://github.com/ReactiveX/rxjs/blob/master/src/operator/do.ts#L13-L14

• Perform a side effect for every emission on the source Observable, but return
• an Observable that is identical to the source.