This repository contains examples of using Observables and Promises in Angular. The examples demonstrate how to work with asynchronous operations using Promises.
When working with Observables in Angular, you may come across two commonly used classes: Subject and BehaviorSubject. While both are implementations of the Observable pattern, they have some differences in terms of functionality and behavior.
A Subject is a type of Observable that allows multiple subscribers to listen to the emitted values. When a new value is emitted, all subscribers will receive the value. However, if a subscriber subscribes after a value has been emitted, it will not receive the previously emitted values.
A BehaviorSubject, on the other hand, extends the functionality of a Subject by allowing subscribers to access the most recent emitted value, even if they subscribe after the value has been emitted. When a new subscriber subscribes to a BehaviorSubject, it immediately receives the last emitted value or an initial value if no value has been emitted yet.
Promises are a core feature of JavaScript that provide a way to handle asynchronous operations. A Promise represents the eventual completion or failure of an asynchronous operation and allows you to handle the result or error once it's available.
Promises have three states:
-
Pending: The initial state. The Promise is still in progress and hasn't been fulfilled or rejected yet.
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Fulfilled: The Promise has been successfully resolved with a value. You can access the resolved value using the
.then()method. -
Rejected: The Promise has encountered an error or failure. You can catch and handle the error using the
.catch()method.