Getting "undefined" in the first time using http .get() in Angular 2

Question

I'm trying to retrieve data from and endpoint in Angular. This is the service:

export class VideosService {
result;
constructor(private http: Http, public router: Router) { }

getVideos() {
    this.http.get('http://localhost:3000/videos?sessionId=' + localStorage.getItem('sessionId'))
        .map(response => response.json())
        .subscribe(result => this.result = result);
        localStorage.setItem('videos', this.result);
        console.log(localStorage);
}

It works everytime EXCEPT the first one. The first one I've got "undefined" and the other one's I get the actual object.

What I'm doing wrong? Thnks!

the other one's I get the actual object No, you get the previous object. — user663031
– user663031, Commented Jul 17, 2017 at 2:53
Possible duplicate of How do I return the response from an Observable/http/async call in angular2? — AVJT82
– AVJT82, Commented Jul 17, 2017 at 9:15

basarat · Accepted Answer · 2017-07-17 02:52:02Z

2

In your code:

.subscribe(result => this.result = result);
localStorage.setItem('videos', this.result);

The code localStorage.setItem('videos', this.result); will execute before .subscribe(result => this.result = result);.

Fix

Lookup async programming JavaScript or simply:

.subscribe(result => {this.result = result;   localStorage.setItem('videos', this.result);});

answered Jul 17, 2017 at 2:52

basarat

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1 Comment

undefined Over a year ago

Exactly, you should also brush up on RxJS Observers, Luis.

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