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What are Asynchronous Operations?

Observable are used to perform asynchronous operations and handle asynchronous data.

What is the difference between Promise and Observable??

What is RxJS?

• RxJS is a javascript library that allow us to work with asynchronous data stream with the help of observables.
• Observables are introduced by RxJS library.
• RxJS stands for Reactive Extensions for Javascript.

What is Observable? How to implement Observable?

Observables are used to stream the data to multiple components.

It is a 3 step process

• Import Observable from RxJS library.
• Create Observable and Emit Data.
• Finally subscribe the Data.

Lets see an example,

app.component.ts

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrl: './app.component.css'
})
export class AppComponent implements OnInit {
  title = 'Demo';

  myObservable = new Observable(observer => {
    console.log("observable start");
    observer.next("a");
    observer.next("b");
    observer.next("c");

  }
  );

  ngOnInit(): void {
    this.myObservable.subscribe(val =>{
      console.log(val);
    });
  }

}

What is the role of HttpClient in Angular?

• HttpClient is a built-in service class available in Angular.
• Its present in @angular/common/http package.
• It performs HTTP requests.