Angular Observable service

Often Observable is preferred over Promise because it provides the features of Promise and more . With Observable it doesn’t matter if you want to handle 0, 1, or multiple events. You can utilize the same API in each case. Observable also has the advantage over Promise to be cancellable.

RxJS (Reactive Extensions for JavaScript) is a library for reactive programming using observables that makes it easier to compose asynchronous or callback-based code . See (RxJS Docs).

It is very easy to display observable in angular using the async pipe . import { Component, OnInit } from ‘@angular/core’; import { Observable, of } from ‘rxjs’; @Component({ selector: ‘app-demo’, templateUrl: ‘./demo. component.

Promises deal with one asynchronous event at a time, while observables handle a sequence of asynchronous events over a period of time .

The biggest difference is that Promises won’t change their value once they have been fulfilled . They can only emit (reject, resolve) a single value. On the other hand, observables can emit multiple results. The subscriber will be receiving results until the observer is completed or unsubscribed from.

Angular Observable use as an interface to handle a variety of common asynchronous operations such as send observable data from child to parent component by defining custom events, handle AJAX or HTTP requests and responses, listen and respond user input in Angular Router and Forms.13 Eki 2019

Angular makes use of observables as an interface to handle a variety of common asynchronous operations . For example: You can define custom events that send observable output data from a child to a parent component. The HTTP module uses observables to handle AJAX requests and responses.