Book Image

Architecting Angular Applications with Redux, RxJS, and NgRx

By : Christoffer Noring
Book Image

Architecting Angular Applications with Redux, RxJS, and NgRx

By: Christoffer Noring

Overview of this book

Managing the state of large-scale web applications is a highly challenging task with the need to align different components, backends, and web workers harmoniously. When it comes to Angular, you can use NgRx, which combines the simplicity of Redux with the reactive programming power of RxJS to build your application architecture, making your code elegant and easy to reason about, debug, and test. In this book, we start by looking at the different ways of architecting Angular applications and some of the patterns that are involved in it. This will be followed by a discussion on one-way data flow, the Flux pattern, and the origin of Redux. The book introduces you to declarative programming or, more precisely, functional programming and talks about its advantages. We then move on to the reactive programming paradigm. Reactive programming is a concept heavily used in Angular and is at the core of NgRx. Later, we look at RxJS, as a library and master it. We thoroughly describe how Redux works and how to implement it from scratch. The two last chapters of the book cover everything NgRx has to offer in terms of core functionality and supporting libraries, including how to build a micro implementation of NgRx. This book will empower you to not only use Redux and NgRx to the fullest, but also feel confident in building your own version, should you need it.
Table of Contents (12 chapters)

Hot, cold, and warm Observables

There are hot, cold, and warm Observables. What do we actually mean by that? For starters, let's say that most things you will deal with are cold Observables. Not helping? If we say that cold Observables are lazy, does that help? No? OK, let's talk about Promises for a second. Promises are hot. They are hot because when we execute their code, it happens straight away. Let's see an example of that:

// hot-cold-warm/promise.js

function getData() {
return new Promise(resolve => {
console.log("this will be printed straight away");
setTimeout(() => resolve("some data"), 3000);

// emits 'some data' after 3 seconds
getData().then(data => console.log("3 seconds later", data));

If you come from a non-RxJS background, you will most likely, at this point, think: OK, yes, that's...