javascript observable
Angular 9 Tutorial | EP16 | rxjs npm (KINDLY SUBSCRIBE)
Complete Playlist: [ Ссылка ]

Part 2: [ Ссылка ]

In this session we will be seeing
Observables in Angular:
way to handle asynchronous programming

ReactX -- asynchronous Programming
Not part of Javascript
Rxjs
Rxjava
Rxpython

Observable
1) Stream of data
2)Observer pattern
2) subscriber subscribed to the Observables can receive data
till the Observables says it is complete or error.

Observables in Angular:
1)EventEmitter @Output
3)Routing - Observables
4)HttpService

complete
Unsubsribing

Creating your own Observable in angular:
import { Component, OnDestroy, OnInit } from '@angular/core';

import { Observable } from 'rxjs/Observable';
import 'rxjs/Rx';
import { Observer } from 'rxjs/Observer';
import { Subscription } from 'rxjs/Subscription';

@Component({
selector: 'app-home',
templateUrl: './home.component.html',
styleUrls: ['./home.component.css']
})
export class HomeComponent implements OnInit, OnDestroy {
numbersObsSubscription: Subscription;
customObsSubscription: Subscription;

constructor() { }

ngOnInit() {
const myNumbers = Observable.interval(1000)
.map(
(data: number) = {
return data * 2;
}
);
this.numbersObsSubscription = myNumbers.subscribe(
(number: number) = {
console.log(number);
}
);

const myObservable = Observable.create((observer: Observer) = {
setTimeout(() = {
observer.next('first package');
}, 2000);
setTimeout(() = {
observer.next('second package');
}, 4000);
setTimeout(() = {
// observer.error('this does not work');
observer.complete();
}, 5000);
setTimeout(() = {
observer.next('third package');
}, 6000);
});
this.customObsSubscription = myObservable.subscribe(
(data: string) = { console.log(data); },
(error: string) = { console.log(error); },
() = { console.log('completed'); }
);
}

ngOnDestroy() {
this.numbersObsSubscription.unsubscribe();
this.customObsSubscription.unsubscribe();
}

}

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