JavaScript Reactive/Asynchronous Code with RxJS 6 & Angular 10: Callbacks, Promises and Observables

Throughout this tutorial, you’ll be introduced to JavaScript reactive and asynchronous code, data streams and RxJS 6 used in Angular.

You’ll learn that reactive programming in JavaScript is about coding with asynchronous data streams and that RxJS is the most popular JavaScript implementation that implements Observables and the observer pattern.

You’ll learne about RxJS operators, the methods that are used to compose Observables and work on their data streams.

Next, you’ll learn that Angular 10/9 uses RxJS v6 for working with asynchronous operations and APIs (instead of callbacks and Promises) in many of its commonly used modules such as HttpClient, Router and Reactive Forms.

#rxjs #javascript #angular

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JavaScript Reactive/Asynchronous Code with RxJS 6 & Angular 10: Callbacks, Promises and Observables

Throughout this tutorial, you’ll be introduced to JavaScript reactive and asynchronous code, data streams and RxJS 6 used in Angular.

You’ll learn that reactive programming in JavaScript is about coding with asynchronous data streams and that RxJS is the most popular JavaScript implementation that implements Observables and the observer pattern.

You’ll learne about RxJS operators, the methods that are used to compose Observables and work on their data streams.

Next, you’ll learn that Angular 10/9 uses RxJS v6 for working with asynchronous operations and APIs (instead of callbacks and Promises) in many of its commonly used modules such as HttpClient, Router and Reactive Forms.

#rxjs #javascript #angular

Angular Meets RxJS: RxJS Operators

Introduction

This article belongs to a series called “Angular meets RxJS” in which I try to explain reactive programming using “RxJS” in an “Angular” context the best I can.

Table of contents

Basic concepts

RxJS subjects

RxJS operators (Part 1)

RxJS operators (Part 2)

RxJS operators (Part 3)

“takeUntil” and the “async” pipe

Higher-order observables

Error handling

RxJS schedulers (coming soon)

Mini-project: Build a Pokedex (coming soon)

In the previous article…

…we talked about functional programming, marble diagrams and creation operators. We used them to create observables out of regular values or by combining other observables. Now, we’re going to see the other type of operators: the pipeable ones. These operators are used to transform an observable into another one.

There are more than a hundred of operators so it’s obvious that I won’t talk about all of them. Indeed, I’ll focus on the most popular and useful ones. However, if you have any question or if you think that I forgot an important one, please tell me in the comments and I’ll update the article.

#angular #reactive-programming #observables #javascript #rxjs

Reactive Programming: Hot Vs. Cold Observables

The Observer Pattern is at the core of reactive programming, and observables come in two flavors: hot and cold. This is not explicit when you are coding, so this article explains how to tell the difference and switch to a hot observable. The focus is on hot observables. The concepts here are relevant to all languages that support reactive programming, but the examples are in C#. It’s critical to understand the distinction before you start doing reactive programming because it will bring you unstuck if you don’t.

Please support this blog by signing up for my course Introduction to Uno Platform.

Reactive Programming

It’s hard to clearly define what Reactive Programming is because it spans so many languages and platforms, and it has overlap with programming constructs like events in C#. I recommend reading through the Wikipedia article because it attempts to give a history of reactive programming and provide objective information.

In a nutshell, reactive programming is about responding to events in the form of sequences (also known as streams) of data. Technically, any programming pattern that deals with this is a form of reactive programming. However, a pattern called the Observer pattern has emerged as the de facto standard for reactive programming. Most programming languages have frameworks for implementing the observer pattern, and the observer pattern has become almost synonymous with reactive programming.

Here are some popular frameworks:

RxJS (JavaScript)

ReactiveUI (.Net)

ReactiveX (Java oriented – with implementations for many platforms)

RxDart (Dart)

The concept is simple. Observables hold information about observers who subscribe to sequences of notifications. The observable is responsible for sending notifications to all of the subscribed observers.

Note: The publish-subscribe (pub/sub pattern) is a closely related pattern, and although technically different, is sometimes used interchangeably with the observer pattern.

Hot Observables

Hot observables start producing notifications independently of subscriptions. Cold observables only produce notifications when there are one or more subscriptions.

Take some time to read up about the observer pattern if you are not familiar. If you start Googling, be prepared for many different interpretations of the meaning. This article explains it well and gives examples in C#. This article is another good article on the topic of hot and cold observables.

A hot observable is simpler because only one process runs to generate the notifications, and this process notifies all the observers. A hot observable can start without any subscribed observers and can continue after the last observer unsubscribes.

On the other hand, a cold observable process generally only starts when a subscription occurs and shuts down when the subscription ends. It can run a process for each subscribed observer. This is for more complex use cases.

#.net #c# #reactive programming #software #.net #dart #hot observable #java #javascript #observable #observer pattern #pubsub #reactive #reactiveui

Wondering how to upgrade your skills in the pandemic? Here's a simple way you can do it.

Corona Virus Pandemic has brought the world to a standstill.

Countries are on a major lockdown. Schools, colleges, theatres, gym, clubs, and all other public places are shut down, the country’s economy is suffering, human health is on stake, people are losing their jobs and nobody knows how worse it can get.

Since most of the places are on lockdown, and you are working from home or have enough time to nourish your skills, then you should use this time wisely! We always complain that we want some ‘time’ to learn and upgrade our knowledge but don’t get it due to our ‘busy schedules’. So, now is the time to make a ‘list of skills’ and learn and upgrade your skills at home!

And for the technology-loving people like us, Knoldus Techhub has already helped us a lot in doing it in a short span of time!

If you are still not aware of it, don’t worry as Georgia Byng has well said,

“No time is better than the present”

– Georgia Byng, a British children’s writer, illustrator, actress and film producer.

No matter if you are a developer (be it front-end or back-end) or a data scientist, tester, or a DevOps person, or, a learner who has a keen interest in technology, Knoldus Techhub has brought it all for you under one common roof.

From technologies like Scala, spark, elastic-search to angular, go, machine learning, it has a total of 20 technologies with some recently added ones i.e. DAML, test automation, snowflake, and ionic.

How to upgrade your skills?

Every technology in Tech-hub has n number of templates. Once you click on any specific technology you’ll be able to see all the templates of that technology. Since these templates are downloadable, you need to provide your email to get the template downloadable link in your mail.

These templates helps you learn the practical implementation of a topic with so much of ease. Using these templates you can learn and kick-start your development in no time.

Apart from your learning, there are some out of the box templates, that can help provide the solution to your business problem that has all the basic dependencies/ implementations already plugged in. Tech hub names these templates as xlr8rs (pronounced as accelerators).

xlr8rs make your development real fast by just adding your core business logic to the template.

If you are looking for a template that’s not available, you can also request a template may be for learning or requesting for a solution to your business problem and tech-hub will connect with you to provide you the solution. Isn’t this helpful 🙂

Confused with which technology to start with?

To keep you updated, the Knoldus tech hub provides you with the information on the most trending technology and the most downloaded templates at present. This you’ll be informed and learn the one that’s most trending.

Since we believe:

“There’s always a scope of improvement“

If you still feel like it isn’t helping you in learning and development, you can provide your feedback in the feedback section in the bottom right corner of the website.

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JavaScript Asynchronous Operation — Read File Directory with Callback or Promises

Asynchronous Operation — Why do we care?

JavaScript is a synchronous, blocking, single threaded language. Synchronous single threaded means JavaScript waits for the task to be completed before being able to move on to the next task. However, Asynchronous JavaScript makes it so much faster if each task takes a really long time! Instead of waiting for the task beforehand to move on, there can be independent threads to start the tasks simultaneously.

http://www.phpmind.com/blog/2017/05/synchronous-and-asynchronous/

In the computer programming world, synchronous and asynchronous may still be considered “fast” in human time. But let’s imagine a scenario if a request was sent to read an entire database of files and there are files in there are REALLY huge therefore take a long time to read. Instead of waiting, what if we can start reading the other files in the directory at the same time. This is Asynchronous JavaScript.

Asynchronous Operation — Code Styles

In JavaScript, functions are first class citizens. This means functions can be treated like values of other types. Functions can be passed to other functions as arguments, returned from other functions as values, and stored in variables.

Async operations are put into an event queue which runs after the main thread has finished processing so that they do not stop subsequent JavaScript from running.

There are 2 main asynchronous concepts that JavaScript uses which leverage functions first class citizenship:

1. Async Callbacks
2. Promises

For other examples, to help you further solidify your understanding of these 2 concepts.

Introducing asynchronous JavaScript

In this article we briefly recap the problems associated with synchronous JavaScript, and take a first look at some of…

developer.mozilla.org

Callbacks, Promises, and Async

Synchronous operations in JavaScript entails having each step of an operation waits for the previous step to execute…

scotch.io

Let’s consider an AJAX (Asynchronous JavaScript and XML) request to the server.

http://www.phpmind.com/blog/2017/05/synchronous-and-asynchronous/

The user clicks on the browser which results in sending an HTTP request to the server to read an entire directory, which could take some time. Instead of having the browser stop running any other functions and wait for the response, another function is set up to wait for this response and react when the response is received.

Let’s see how we can write these Asynchronous Operations.

#programming #javascript #asynchronous #promises #coding