Front end web developer. No setup configuration. By using React, we can easily create/compose asynchronous or callback-based code. When doing FRP we try to specify how the value of a variable is going to change over time at declaration time. They reached a point where it wasn't feasible to only rely on React's state management. RxJS Tutorial: Observables, Operators and beyond. We're a place where coders share, stay up-to-date and grow their careers. RxJS is perfect for complex asynchronous queries and reactions to events. But, it is a good starting point to understand what it takes to use RxJS Observables in React. Later, we will use both values to operate on them with yet another observable: As you can see, the subject can be used to adjust the API URL. jasonwatmore.com. What's missing in this React component is the state management. The initial discussion was about Redux or MobX for a more sophisticated state management. This website is not affiliated with Stack Overflow. I am by no means an expert with RxJS, just learning it myself, and maybe some people can help me out here and there, but in the end, I just hope to offer you inspiration on how to do things differently in React. We will build a small game during this tutorial. It only passes its own state and props to the input component which is going to be enhanced by it. Would be glad to know your thoughts! With RxJS and lodash, it is easy to write clean code in these cases. In this last section, let's take this URL to fetch data from this API URL. Next, pretend having the array of stories at your disposal in the App component to display them. Feel free to compare two codebases that do the same thing. In both cases I have no idea how to bind React events with rxjs. Ok, I get it. Since I am not sure how to retrieve the values from the query and subject observables immediately in the higher-order component to set them as local state, I would provide an initial state for the higher-order component again. RxJS is perfect for complex asynchronous queries and reactions to events. BehaviorSubjects are useful for representing "values over time".". In my following example I will show how to wire this up between two React components. Doing it with this workaround, it receives a default parameter. However, few popular programming languages come equipped with the reactive API by default. But that's not the approach we are going to use here. Now you can provide the initial state as third argument to the higher-order component. I am by no means an expert with RxJS, just learning it myself, and maybe some people can help me out here and there, but in the end, I just hope to offer you inspiration on how to do things differently in React. Receiving and altering state happens via RxJS observables even though the higher-order component uses React's local state internally. Let's implement it: The higher-order component receives the observable and the object of triggers (perhaps there is a better term in RxJS lingua for it) in its function signature. -- When we subscribe to greeting$, // ✏️: "Hello, World!" -- When we subscribe to greeting$, // ✅: "Hello, Thundercat!" RxJS is a library for Functional Reactive Programming (FRP from now on) in JavaScript. Considering what we know so far. What bothers me now is that the initial state is somehow defined in the declaration of the query$ and subject$ observables too. 542. Something interesting about the dependency array of React hooks: The hook callback will be executed only when its dependencies change, and React tracks these changes by just doing plain old value comparison. 3 responses. The below example contains a Home component that sends messages to an App component via a message service using RxJS. RxJS is a library for composing asynchronous programming. RxJs makes implementing pub sub a breeze! If you google what is FRP, you'll probably find a lot of really cool definitions, each one a little bit more complex than the previous one. After all, I hope you enjoyed going through this tutorial with me. This post is intended for those with React and RxJS experience. Click that Subscribe button -- I will be focusing on more RxJS soon.Also, there's a full written version of this course, and here they are:1. In our new generated app directory, let’s navigate to /src/. MobX is a state management solution. Father. Bits and Pieces. you said: "I do not always agree with my thoughts." This section contains all RxJS operators, included with clear, executable examples.Links to additional resources and recipes for each operator are also provided, when applicable. In our initial example we are only interested in calling getSomeName once, so let's forget about this alternative. Also, all hooks created with React-RxJS can be … The onSelectSubject() trigger isn't anything new. You’ll see a lot more of that "symbiosis" as we go on. Also use observables for lifecycle hooks ; External References. Sometimes you don't need Redux or MobX, but maybe observables with RxJS might be the right fit for your application. Written by. Reactive programming is a declarative programming paradigm that deals with the flow of data in “streams” and with its propagation and changes. Let's see how we can do this with a higher-order component. It is a standalone pure technical solution without being opinionated about the architectural state management app design. # functional # javascript # react # tutorial. Beware: I mostly tweet JavaScript rants on Spanish. DEV Community © 2016 - 2021. The final Rx.js in React example with the higher-order component can be found in this GitHub repository. Made with love and Ruby on Rails. Operators are the horse-power behind observables, providing an elegant, declarative solution to complex asynchronous tasks. By having the last argument of the combineLatest() function, you can map it directly to a property name called stories. However, they had also a prototype for a React application with RxJS. No tooling. Where RxJS shines is that an event is an arbitraty event, you can opt to send data with the event, so that observers can instantly consume the new state without querying the store: RxJS is a JavaScript library for the reactive programming using Observables, which makes easier to work with asynchronous or callback-based code. With React, it is great for creating communication between components. Email: tutorialpedia@outlook.com. With that being said, the strategy to use RxJS with React is basically by deferring the way we handle these (side) effects from React to RxJS. This course is a practical guide to learning the RxJs library (Reactive Extensions for Javascript). Out GreetSomeone component receives greet from props and name is the result of a promise returned by calling fetchSomeName. We will not get into the installation process for Reactjs here, to know about ReactJS Installation re rxjs documentation: Getting started with rxjs. React RxJS; React is an open-source JavaScript library. You will start by learning a couple of baseline concepts, and then learn an extended catalog of RxJs operators. In the end, when subscribing to this new observable, every time a new subject or query from the other observables is provided, a new request is made and the result end up in the function of the subscription eventually. At first sight, RxJS is blown up lodash but for dealing also with async. The middleware can be used in Redux applications. en English (en) Français (fr) Español (es) ... react-native; TypeScript; This modified text is an extract of the original Stack Overflow Documentation created by following contributors and released under CC BY-SA 3.0. Maybe someone of you help me out here and teach me RxJS :). The RxJS HOC is not doing anything yet. Recently a client of mine inspired me to learn RxJS for State Management in React. If you know another way of doing it, you canleave me a comment below. What this actually means is that if we have an object as a dependency, and the reference to that object doesn't change, it doesn't matter how the inner properties of that object change: the hook simply will not be executed. Managing application state is one of the hardest parts of writing an application. Justin Mitchell. Check out these other great resources! You can see a working demo here. Now, the initial values for the query and subject that we are seeing when the App component renders for the first time are not the ones from the initial observable values: The subject is undefined and the query is an empty string, because that's what we have provided as default parameter for the destructuring in the function signature of the App component. The challenges: In conclusion, the challenge was not about React itself, even though I was able to help here and there with it, but managing everything behind the scenes that couple the cryptocurrency domain to React. GitHub React-RxJS. and I had a good laugh, thanks :-), Nice article, Osman! The app component displays messages it receives as bootstrap alerts at the top of the screen. We'll start by copying all of our RxJS code inside our GreetSomeone component. The triggers are only passed through the HOC to the input component. … Once you subscribe to the observable, when either one of the values (query, subject) changes, the subscription will receive both values. 2. RxJS is a library for reactive programming using Observables, to make it easier to compose asynchronous or callback-based code. Music lover. React-RxJS website JavaScript 4 0 0 0 Updated Jan 5, 2021. rxjs-traces Utility to trace references between observables. Originally published by Scott Lively on June 26th 2017 9,828 reads @scott.livelyScott Lively. Justin Mitchell. Although this solves our problem, it could have some unexpected consequences. This article was originally posted on Spanish in my blog. Either you search for stories by popularity or by date. That's why I have used React's local state as intermediate layer which triggers comfortably a re-render for us as well. Now you have constructed your API URL with two values from a combined observable which encapsulates two observables. add a comment | 4 Answers Active Oldest Votes. We strive for transparency and don't collect excess data. Get Started. Side Notes. This is because our greet$ Observable is defined when the useEffect callback is executed, and this just happens once. Templates let you quickly answer FAQs or store snippets for re-use. The callback function we pass to useEffect runs after render, while the useMemo variable is calculated before render. How to refactor RxJS observables with React hooks Examples are always better than words, so today we will be working on a simple app that will … By using React, we can easily create interactive UIs. Michal Zalecki on 23 Mar 2016 (updated 11 Nov 2017) in #JavaScript, #RxJS, #React. The sample application is pretty straightforward. It stores the latest value emitted to its consumers, and whenever a new Observer subscribes, it will immediately receive the "current value" from the BehaviorSubject. In this post I will show how to use RxJs to implement pub sub in React components. It's error prone, because the observable initialization and the initial state for the higher-order component share the same values. This is a quick tutorial to show how you can communicate between components with React Hooks and RxJS. Even though only one of the values changes, the other value has still the old value from before, because combineLatest always combines the latest emitted values from the observable streams. This site focuses on making these concepts approachable, the examples clear and easy to explore, and features references throughout to the best RxJS related material on the web. In the case of useMemo, this is conveniently handled by React. Learning RxJS and reactive programming is hard. In our case, we want to have them as an object to destructure them as before in the higher-order component to React's local state. 373 2 2 silver badges 9 9 bronze badges. The tutorial example uses Webpack 4 for compiling + bundling the React components and is styled with bootstrap 4. Wonderful! In this tutorial, I want to guide you through building a simple application with RxJS in React. The next method exists on the observer, not the observable. In our case, the value of greeting will be recomputed depending on the values of greet and name. I've been looking online and all react/rxjs tutorials just use subjects without explaining why. I do not always agree with my thoughts. Then push all state and business logic to the observables. Move into the directory: cd react-prj. # functional # javascript # react # tutorial. First, our main useEffect callback just runs once: Hooray! As you can see, the higher-order component will manage React state eventually. Each story in the list of stories has a fallback property due to inconsistencies in the API. You may be comfortable with data fetching in React, but when using RxJS observables you have to add yet another observable stream to your composition. Let's say we have an application which will make a request to a third-party API eventually. The observable can be used to wire up the App component with the higher-order component. and I surely love Rx in React posts . One small change in the App component let's get you away with not setting an initial state for the query property in the higher-order component. However, useMemo only lets us define greeting when greet and name change, but it doesn't provide any information about where and how those values change and how they are updated. Observable: The query argument is an observable which has an initial value, but also emits its new values over time (hence the BehaviorSubject). Tip. One thing we could do is add greet as a dependency to useEffect, making sure that the callback is executed every time greet changes. It uses the combineLatest function from RxJS to combine the latest emitted values of two (or more) observable streams. React + Typescript + RxJS. It should provide you a different perspective on working with React. But how this is better if we have more code? DEV Community – A constructive and inclusive social network for software developers. RxJS Reactive Extensions Library for JavaScript. The essence of FRP is to specify the dynamic behavior of a value when declaring it This is a quick tutorial to show how you can communicate between components in React with RxJS. Also we don't want to trigger it if the value is an empty string. Let's introduce a second value stream that can be manipulated in the App component similar to the query property. The same applies for the written tutorial where I might have misused some RxJS lingua. It might seem rather strange how code like this would look, since JavaScript doesn't have primitives for doing something like this (generators is the closest thing I can think of). By using RxJS we can express the async dynamic behavior of our state in a more declarative fashion, by using function composition and other fancy functional programming techniques. I would love to retrieve the initial values from the observables in the higher-order component to set the initial state instead. There's the multitude of concepts, large API surface, and fundamental shift in mindset from an imperative to declarative style. – Josh Pittman Oct 14 at 2:24. add a comment | 1 Answer active oldest votes. However, when clicking one of the buttons for the subject, the request should be executed immediately. Within the observable subscription, the function only pushes all incoming values from the stream to React's local state with this.setState(). I couldn't find a quick solution on how to stream the values from the observables subscription directly to the props of the enhanced component (App). Learn React by building real world applications. The effect callback will be executed EVERY time greet changes. Now you can provide the new observable to your higher-order component again. I rewrote the Redux tutorial using the RxJS Hooks approach. The below example contains a Home component that sends messages to an App component via a message service using RxJS. React bindings for RxJS. The million dollar question is: How and where do these dependencies change? React-RxJS. In other words, during the first render the value of greeting with useMemo will already be computed; whilst in our useEffect version, its value on the first render will be the value defined with our useState. Here you can specify how you want the emitted values from the observables to be returned. If you have any idea on how to improve it, please let me know. 9. If you want, you can implement the following logic in your App component too, but you will most likely extract it as a reusable higher-order component (HOC) at some point anyway. This will generate a new react application using create-react-app. Let's take a look at the same example using rxjs-hooks: You can look at their documentation to understand what useObservable does under the hood. The application was a marketplace for cryptocurrencies which had lots of real-time widgets. Every time you change the value in the input element (query) or click a button (subject), the fetch observable is triggered again with the latest values from both streams. Ryan Thelin. Difference between React and RxJS. RxJS is a library for Functional Reactive Programming (FRP from now on) in JavaScript. Can't get enough RxJS? We install the rxjs library: npm i rxjs. If you google what is FRP, you'll probably find a lot of really cool definitions, each one a little bit more complex than the previous one. Let's get away from React for a while and let's see if we can express greeting (and fulfill our FRP definition) using RxJS. Next, introduce another observable that can be used to change the subject. In reality, it is so much more than that. Do we need state management libraries? It also lets us define really complex async logic that would be a nightmare to handle using plain old Promises. We'll start by defining two Observables that will emit the values of greet and name, and we will compose them to get another Observable back that will represent how greeting changes over time: In our React example the value of name came from a Promise. The changed values are displayed with the API URL. rxjs documentation: Getting started with rxjs. Before We Start the Tutorial . Chidume Nnamdi Follow. Let's introduce a way on how to manage state in React with RxJS by having a higher-order component for it. Although there is some friction when using RxJS inside React, hooks play a great role in order to improve the way both libraries operate together. Fair enough, greeting is just the result of a simple expression `${greet}, ${name}!`, but it turns out we control when its value is recomputed by using useMemo, which is convenient for our definition of reactivity. It’s often the first created component of any application, but tends to suffer from application growth. This tutorial doesn’t assume any existing React knowledge. Truly reactive. That's why the App component receives straight forward the onChangeQuery() function which operates directly on the observable to push a new value to it. Source code for the Redux Toolkit Advanced Tutorial - re-rxjs/react-rxjs-github-issues-example : It subscribes and displays in-place values from it's stream(s). Before we can do this request, we have to capture a search term that is used for the data fetching to create the API URL. The best of web development articles, tutorials, and… Follow. However, we may not want to trigger the fetch observable every time the value in the input element is changed. RxJs 6 In Practice (with FREE E-Book) by Angular University will help you learn RxJs and Reactive Programming. The fact we can describe a state update inside a useEffect callback, is just pointing out that updating state is in practice a "side effect", as in it is affecting the real world. When you run your application again, you should be able to change both values via the input element and the button elements. Handling Observables with NgFor and the Async Pipe . We store our subject with useRef, which lets us persist our reference between renders. Tutorials. The App component only receives the query state and the onChangeQuery function to alter the state from the HOC as props. Tweet. An addition to the combineLatest function is its last argument. Continuing with our refactoring, we can extract the definition of name$ from the useEffect callback (we can actually extract it from out component entirely, FWIW). Lately I’ve been trying out React, Typescript, and RxJS and so far I really like the result. Learn React like 50.000+ readers. If you don't have create-react-app first, install it globally: npm i create-react-app -g. Then, scaffold the React project: create-react-app react-prj. That's where RxJS got interesting and the prototype they showed me looked really promising. My favorite definition of FRP is: The essence of FRP is to specify the dynamic behavior of a value when declaring it This section provides an overview of what rxjs is, and why a developer might want to use it. Although the definition of greeting hasn't changed, we cannot determine just by reading it that one of the values on the dependency array comes from a Promise and that by extent, is async. The debounce happens when entering something in the input element now. Otherwise, the props passed to the App component wouldn't work. However, so far the higher-order component is a black box for us. Enjoy? 3. In JavaScript there are no primitives for determining the async nature of this expression (neither in React). We are using a flatMap() instead of a map() operator for accessing the result of the resolved promise and not the returned promise itself. >npm i -g create-react-app. The Redux Observable RxJS: Going Epic tutorial will show you how to reactive programming in Redux. Then push all state and business logic to the observables. Using subjects:Fiddle. The concepts and APIs in RxJS and React are very compatible: the way useEffect aligns with an RxJS subscription and how the clean-up call is a perfect time to unsubscribe. The techniques you’ll learn in the tutorial are fundamental to building any React app, and mastering it will give you a deep understanding of React. rxjs-react-component. In RxJS land, defining the async nature of name is quite simple, we only have to create an Observable from fetchSomeName and handle weather the Promise is resolved or rejected in the following way: And that is all it take to define the async nature of name$ and by extent, the async nature of greeting$. What do you think if we complete subject on unmount (just to be safe): Just today I've published an article with a bit different approach to RxJS consumption in React: a fragment that observes it's RxJS children, e.g. This tutorial is no introduction to RxJS but only one of many ways of using RxJS with React. And that could be all, folks, and we'd live happily ever after. Instead, we want to manage the state somehow with RxJS. When I did a code audit for their application, they wanted to get my opinion about how to proceed with it after only using React's local state. They had built a prototype for each of these technologies. This courses takes a practical example based approach. Reactive programming is an event-based paradigm that allows us to run asynchronous sequences of events as soon as data is pushed to a consumer. And voilá, that's all for today. The new observable is again a combination of the subject and query observables, because we need both values to create the API URL which we need for the actual data request. Rxjs offers us a different type of functions to create a new observable. Another way of coping with this problem would have been to set an initial state for the query component in the higher-order component: If you try your application, the input field should work. RIP Tutorial. Published: 07/06/2017. Lately I’ve been trying out React, Typescript, and RxJS and so far I really like the result.The basic premise was to have a single observable library and connect that to React to update components. With you every step of your journey. Within the pipe() method of the observable, we can apply so called RxJS operators to do something with the values. Create a React app using create-react-app. Now, the crucial implementation of the new observable that fetches the data for React to display it. Share. With React, it is great for creating communication between components. Any change to greet will not be propagated to greet$, and by extension neither greeting$ will know about it. 542 claps. We've specified the dynamic behavior of greeting$ at its definition place. 19) What do you understand by the term Non-Blocking in RxJS? It will allow you to expose observables that maps to state changes. It's an object, because we may want to pass more of these functions that are doing something with the observables to the higher-order component. We have only passed two arguments to the higher-order component. RxJS, ggplot2, Python Data Persistence, Caffe2, PyBrain, Python Data Access, H2O, Colab, Theano, Flutter, KNime, Mean.js, Weka, Solidity Reactive programming is an essential part of modern web applications. This website requires JavaScript. Angular ; TypeScript ; RxJS ; React ; JavaScript ; HTML ; CSS ; Importing and using NPM packages in Deno . For example: Although in practice both snippets yield similar results, there are a couple of substantial differences on how they do it. A subject is both an observer and an observable, hence it has a next method. Consider the following example: useMemo lets us define a computed value that will be recalculated whenever their dependencies change. One problem with our current solution is that if the of value of greet changes, greeting will not be recomputed. Anyone can subscribe to this observable. In this case we map from the two values to a request with axios to the result. How to refactor RxJS observables with React hooks Examples are always better than words, so today we will be working on a simple app that will … Source code for the Redux Toolkit Advanced Tutorial - re-rxjs/react-rxjs-github-issues-example Built on Forem — the open source software that powers DEV and other inclusive communities. Afterward, again a rerender runs as before. In this tutorial, I want to guide you through building a simple application with RxJS in React. Then we can leave out the default parameters for the App component too. In JavaScript, primitive values are equal when their values are equal (5 is always equal to 5) but things like objects are only equal if they point to the same reference (memory address, call it whatever you like). Second, we can hide the implementation details using a custom hook: useObservedValue returns the memoized value of subject.current.asObservable() to discourage emitting values manually on our Subject using next. This article is not a tutorial about React nor about RxJS, but just some of my thoughts about how to use RxJS on React applications. You could also implement a render prop component instead. Use RxJS with React. -- When `fetchSomeName()` is resolved, // ❌: "Hello, Mololongo!" The solution I've implemented is not the cleanest and has a lot of rough edges. While RxJS is typically thought of as being used with Angular projects, it's a completely separate library that can be used with other JavaScript frameworks like React and Vue. If you like how the higher-order component is used to store state in this tutorial, checkout this tutorial where we will build a GraphQL client with render prop components together. Docs; Tutorial; API; GitHub; Black Lives Matter.Support the Equal Justice Initiative. RxJS allows you to create reactive programs with JavaScript to better serve your users. JavaScript; Nodejs; React; Reactive Programming; Rxjs; 542 claps. You can use RxJS to process and throttle user events and as a result, update the state of the application. // =>: "Hello, World!" However, the observable passed to the higher-order component is something new. Sep 29, 2020 - 10 min read. Seamless React integration React-RxJS offers a hook-based API with first-class support for React.Suspense and Error Boundaries. In my view it’s one of the major strengths of the framework. With RxJS Subjects and React Hooks we get the one principle out of the box – the pure-functions, as observable streams are themselves pure-functions. By using the buttons, it can be used to switch between the two subjects. Explanation from the RxJS documentation about the BehaviorSubject: "One of the variants of Subjects is the BehaviorSubject, which has a notion of "the current value". That's why we can enhance the query observable to debounce (operator) the request (only the last emitted event is taken after a threshold of time) and to filter (operator) out every stream event where the query string is empty. A quick tutorial and example of how to communicate between components in React using RxJS Observable and Subject. – Heinrich Apfelmus. What we'll do then, is define greet$ as a BehaviorSubject (using a ref) that will emit values whenever greet changes: BehaviorSubject is kinda like an event emitter which we can subscribe to (just like we do with regular Observables), but as with any event emitter, we con produce values imperatively calling the next method. If you wouldn't apply this change, the query property would be undefined in the beginning. An aside about useEffect. However, this state will be derived from an observable stream. It will only run when the variable we are observing points to a different reference. The initial { query: '', subject: 'search' } object and all further objects being emitted from the combined observable stream are sufficient for the higher-order component to destructure these values into React's local state. To start our application, let’s navigate to our new app directory and run the command npm start: cd rxjs_react_chat npm start. Next: create-react-app rxjs_react_chat. I think somebody brought to my attention that using components with subjects makes them tightly coupled. Observing points to a different reference Practice ( with FREE E-Book ) by Angular University will you! My blog to improve it, the query $ and subject $ observables too ` (. One of the query state and props to the App component with the reactive API default. A more sophisticated state management tutorial ( robinwieruch.de ) Oct 22, 2018 social network software... A Home component that sends messages to an App component to set the initial state one... Rxjs hooks approach being opinionated about the architectural state management Community – a constructive and inclusive social network software! Is whether the user will see any input changes during debounce Community – a and. ; GitHub ; black Lives Matter.Support the Equal Justice Initiative, World! application! Encapsulate this with a higher-order component again External References RxJS with ReactJS value when it... A practical guide to learning the RxJS library: NPM I RxJS that! What state you want the emitted values from the observables surface, and experience! A value when declaring it – Heinrich Apfelmus will see how to use to... The approach we are observing points to a property name called stories for us example with the of! Result, update the state dependent on that call they are already used in the beginning a way how. But with some limitations us persist our reference between renders a structure now, you can provide initial. These cases stream that can be used to switch between the two subjects good. Value of a promise returned by calling fetchSomeName after all, World! 2020 ) → 8 read... Programming languages come equipped with the reactive API by default that useMemo is kind equivalent. Non-Blocking in RxJS to happen to prevent memory leaks useEffect callback just runs once: Hooray there 's the of. You want the emitted values of greet and name is the result a JavaScript library Functional! Reactive Extensions for JavaScript ) overview of what RxJS is blown up lodash for. Free to compare two codebases that do the same thing fit for your application the essence of FRP to. The values it if the value of a promise returned by calling fetchSomeName leave out default! Coders share, stay up-to-date and grow their careers a good laugh, thanks: )! Is kind of equivalent to useState + useEffect inclusive social network for software.... Better serve your users a practical guide to learning the RxJS hooks approach hook. Is a declarative programming paradigm that deals with the onChangeQuery function value in the higher-order component different reference we from! Below example contains a Home component that sends messages to an App component only receives the query property be... Really like the result to specify the dynamic behavior of a promise returned by calling fetchSomeName quickly answer or. Web applications and as a result, update the state of the screen a way on to! To expose observables that maps to state changes our case, the higher-order component with... Nightmare to handle using plain old Promises of FRP is to specify rxjs tutorial react value. Your users that can be found in this tutorial with me it could have some unexpected.... Will know about it it ’ s often the first created component of any application, but maybe with! Why a developer might want to trigger the fetch observable every time the value of variable. As third argument to the combineLatest function from RxJS to combine the latest emitted values of two or... Somehow with RxJS a prototype for a more sophisticated state management query value work... To events 2020 ) → 8 min read ( updated 11 Nov 2017 ) in # JavaScript, React... Just happens once queries and reactions to events that could satisfy this definition, but maybe with. To reactive programming is an open-source JavaScript library for the written tutorial where I might have misused RxJS. Soon as data is pushed to a different reference question, it is library. Original Redux Reddit tutorial and example of how to wire up the component... Reference between renders to make it easier to work with asynchronous or callback-based.!