Shulou(Shulou.com)06/01 Report--

This article focuses on "how to apply reactive programming in Node.js". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to apply reactive programming in Node.js.

Reactive programming provides advanced data streams that can create and manipulate event streams in a predictable way.

What is reactive programming?

In short, a program can be said to be reactive when a change in input leads to a corresponding change in output without the need to manually update the change in output. This allows software engineers to bypass the pressure of dealing with huge implementations manually.

The functional reactive programming paradigm makes our reactive code base easy to read and understand because it reduces callback hell, which makes asynchronous code blocks difficult to read.

Because reactive programming has a lot to do with asynchronous operations, the functional approach makes it easier to determine the results of asynchronous operations.

The basic principles of reactive programming operators

Operators are methods that Observables relies heavily on. They have the following usage.

Convert an asynchronous event to Observables when processing an asynchronous request

Combine the sequences of multiple observable variables into a single observable variable

Error handling

Dealing with time-based operations

Observable operators include [filter (...)] (https://rxjs.dev/api/operators/filter),[mergeMap(...)](https://rxjs.dev/api/operators/mergeMap),[of](https://rxjs.dev/api/index/function/of),[from](https://rxjs.dev/api/index/function/from),[concat](https://rxjs.dev/api/index/function/concat) methods, etc.).

Observable flow

An Observable stream is an array of input values that are processed over time. An Observable sends events to its subscribers, who in turn listen to these events for further processing. Observable streams can be combined to create new streams. Array methods, such as map,reduce,filter, and so on, are used to manipulate streams.

Values can be transmitted to subscribers in the following ways.

Import {of, Observable} from "rxjs"; const emitter: Observable = of ("Sam", "Ray", "Thomas"); subscriber

Observable subscribers are more like array iterators. They cycle through the resulting Observable streams, making it possible to convert or process each stream.

The following segment shows how to subscribe to an Observable stream.

Emitter.subscribe ((value: string) = > {console.log (`Name: ${value} `)})

Reactive programming has built-in subscription methods, such as emit and flatMap map methods, which allow us to listen to every value of the Observatory stream and process them according to our needs.

Standard for reactive systems

A fully reactive Node.js system should meet the following criteria.

Responsive architecture

A reactive system should have a good user experience and provide a timely response to user interaction.

Elastic architecture

The elastic architecture, if implemented correctly, will allow the system to respond to errors without destroying the entire system.

This architecture ensures that each node has a replica. If the primary node fails, there will be some kind of fallback on other available nodes.

Expandability

The system should be able to handle different loads, which is related to its ability to scale down when the infrastructure needs little or no resources, and when the infrastructure needs more resources, it can scale up to provide an effective cost management strategy.

In addition, the system should also be able to handle load at a point in time.

Why consider Node.js reactive programming?

Now that we have briefly discussed the fundamentals of reactive programming, it is also important to understand the reasons for considering a reactive approach to programming in Node.js.

Expandability

Writing functional reactive code makes it easier to manage the code base and improve the scalability of the project.

Function realization

For projects that need to modify functionality or add new features on a regular basis, writing functional reactive code makes it easier for new features to be added to existing projects.

Intricate issues related to time

We do encounter some time constraints when making asynchronous requests to an external API. These limitations can be effectively addressed by reactive programming.

Reduce the verbosity of the code

Implementing the reactive programming paradigm will greatly reduce the amount of code required to implement specific functions.

Introduce coordination and its benefits / tradeoffs

Before reactive programming was born, building microservices with Node.js required a coordinator pattern that coordinated the interaction of all services.

A typical use case of the coordinator pattern is to have microservices in an e-commerce application that sequentially process the following tasks: get a customer order from the shopping cart, calculate the total amount, generate a bill, update the product inventory and create an order ID, and provide the Pending to the seller after successful payment.

While this provides a systematic way to deal with the logical flow of an application, a major disadvantage of tight coupling of dependencies can damage the entire system. For example, if the previous service fails, all dependent services will not be executed.

When to use reactive programming in Node.js

Reactive programming is not a panacea, but it is very appropriate in certain situations.

The reactive programming model is appropriate when the application flow needs to be dispersed into manageable microservices.

When the application needs to be delivered to production in a limited time

When the temporary shutdown of a previous dependency will cause the entire system to crash

Reactive programming is also appropriate when there are many asynchronous code blocks and waiting results may be delayed.

Disadvantages of reactive programming in Node.js

Although the functional reactive programming approach reduces the shortcomings encountered by the coordinator mode, it cannot replace the coordinator mode because it has its own shortcomings.

Redundant blocks of code generated by decomposing the application process and distributing it across all services

In order to build reactive services, you need a comprehensive understanding of convection and event loops.

RxJS, a popular reactive programming library in Node.js

This is one of the most popular reactive programming libraries in JavaScript and is actively maintained.

At the time of this writing, RxJS is transitioning from V7 to V8, which was downloaded more than 27 million times last week. This transition is characterized by rewriting library performance, better modularity, better debuggable call stack, and backward compatibility.

Here is a quick example of using RxJS.

Import {range} from "rxjs"; import {map, filter} from "rxjs/operators"; range (1200) .pipe (filter (result = > result% 2 = 1), map (result = > result * 2)) .subscribe (result = > console.log (result)); Reactor.js

Reactor.js is another JavaScript library for reactive programming. Although it is not very popular compared with Bacon.js and Rxjs, it is famous for its lightweight. It is much easier to use Reactor.js to maintain consistency in complex data models because it automatically tracks reactive variables and retriggers the observer when the value of any reactive variable changes.

With Reactor.js, you don't need to set up subscriptions / listeners manually, because dependencies are automatically set for you.

Here is a quick example of Reactor.js usage.

Const reactor = new Reactor ({name: "Doe"}); observe (() = > {console.log ("My name is", reactor.name);}); / / prints "My name is Doe" reactor.name = "John"; / / prints "My name is John"

Reactor is based on the same reactive principle as Bacon.js and Knockout.js.

Other JavaScript libraries for reactive programming include.

Flyd

Bacon.js

Knockout.js

Kefir

Majority

At this point, I believe you have a deeper understanding of "how to apply reactive programming in Node.js". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.