Module 04 RxJS

Module 04 - Reactive X in JS (RxJS)


fun-with-rxjs	Introduction to Observables, Subjects, And Reactive X
reactive-colors	Demonstrates asynchronous operators on real life example
tv-maze-http	Introduction to the `HttpClient` Module

We understood the meaning of a Stream
We defined what an Observer<T> is and understood that it has 3 methods
- next(T)
- complete()
- error(err)
We understood that Observable<T> is an object that allows observers to subscribe
- subscribe(Observer<T>)
We saw how to define an observer explicitly by supplying the 3 methods and their implementation
We saw how to create an observable using the interval operator
We saw that 2 observers that subscribe on different times, get different sets of events that are not synchronized
We understoof the difference between cold observables and warm observables
We saw how to create a custom observable using the observable constructor
We got familiar with the Subject object and understood that it is basically an event...
We learned about BehaviorSubject and understood that it is just a subject that sends the latest event to a new observer on the moment of subscription
We learned how to develop stateful services using BehaviorSubject and expose it as an observable using the .asObservable() method
We understood that if we subscribe to an observable we must also unsubscribe from it when we are done with it to avoid memory leaks
We saw that we can bind directly to an observable using the async pipe in the html

We talked about the concept of operators in math, strings and arrays
We understood that RxJS operators create observables.
We saw 3 documentation web sites that serve as reference guide for reactive operators
We covered some simple operators
- map
- from
- interval
- filter
- take
- takeLast
- skip
- skipLast
- merge
We created an example that uses observable to convert user search keyword into a list of matching results (Colors)
We Understood that the map operator cannot be used when we apply an asyncronous function on each event because it creates an Observable of Promises
We saw how to use mergeMap and SwitchMap as asynchronous alternative for map when using async projections
We understood the difference between mergeMap and switchMap

We discussed internet protocols: IP, TCP, UDP, HTTP, FTP
We talked about the structure of Http Request - Verb, URL, Header, Body
We talked about the various types of verbs:
- GET to query a single or a list of objects
- POST to add a new object
- PUT to update an entire existing object
- DELETE to delete an existing object or list of objects
- PATCH to modify a part of an existing object (several fields only)
We saw how to use Postman To test web APIs
We used HttpClientModule to provide our services with the HttpClient service
We used the HttpClient Service to create web requests to an online api called TV Maze
We saw that the HttpClient methods all return Observables
- Which means that no request happens until we subscribe
- Which also means that if we subscribe 3 times, we run the request 3 times...
We saw that it is preferable to use the toPromise operator, to convert the observable to promise.
We saw that the async pipe also works with promises...
We saw how to use sites like QuickType to automatically generate model for json data

Introduce the Router - a tool used to navigate between pages in an angular application
Understand how to divide the application into Modules and the various types of modules
Talk about advanced routing features: Guards, Nested Routing, and lazy loading