I had an interview, where the interviewer asked me if redux uses context API internally. Pls provide a detailed description if yes. Thanks
Redux doesn't use context api, it's a javascript library for state management. You can use Redux with any application- like (react, angular, vue, svelte, etc). However, for using redux with react applications, you need react-redux which is the official react bindings for redux.
react-redux uses React's context api to make the redux store accessible to all components. The reason why you need react-redux is because, React uses virtual dom - which means you can't manipulate the DOM directly. In other libraries like angular, we use the NgRx library (For angular).
Internally, React Redux uses React's "context" feature to make the
Redux store accessible to deeply nested connected components. As of
React Redux version 6, this is normally handled by a single default
context object instance generated by React.createContext(), called
ReactReduxContext.
Source
Yes, but differently than if you would be doing it by yourself.
If you were to use Context manually, you would usually do value propagation - passing the current state value down the tree. This can lead to very inefficient rerendering behaviour. See this article for a deeper explanation.
React-Redux on the other hand uses context for dependency injection. The store is passed down the tree and will never change, never triggering a rerender. All the rest is done by Redux internally, using manual subscriptions. This is much more performant.
Related
What is the basic difference between react and redux? is react and redux is same? why we should use redux? Finally why it's called react-redux?
I want to know this i just confused between this two.
You must be pretty new to web development. First of all, welcome !
React and redux are pretty different beasts, but have often been used together to make state management easier in React apps.
React is a front-end web framework, it allows you to create a wide range of web apps using JSX (React's way of fusing Javascript and HTML). This is a gross oversimplification, I encourage you to read the documentation.
Redux is a state management library. With it, you can define one or many stores, containing a state (basically an object that holds any data you need), actions (methods to alter or retrieve the current value of the store) and to subscribe the state's changes at a global level. Again, the Redux documentation should have most of the answers you're looking for.
React and redux are often used together, mainly through the use of the react-redux package, since Redux offers a global, reactive state, enabling you to share data between React components anywhere in your app without having to pass props.
Now tough, you could achieve similar functionnality without Redux entirely, using React's own Hook and Context APIs. Although the logic behind these is a bit more involved, it allows for far more flexibility.
I am building a web app where redux is configured and app is fairly large.
Now I want to store some user preferences which will be available as part of an API respopse.
As this data is required to the majority of components I am planning to store data in the context and wrap application using the context.
I have Few questions regarding approach.
Will considering context impact the performance?
As Redux is already configured which internally uses the Context. So should we continue to use redux for user data.
Is it good practice to use Redux and Context together.
Context and Redux are very different tools that solve different problems, with some overlap.
Context is not a "state management" tool. It's a Dependency Injection mechanism, whose only purpose is to make a single value accessible to a nested tree of React components. It's up to you to decide what that value is, and how it's created. Typically, that's done using data from React component state, ie, useState and useReducer. So, you're actually doing all the "state management" yourself - Context just gives you a way to pass it down the tree.
Redux is a library and a pattern for separating your state update logic from the rest of your app, and making it easy to trace when/where/why/how your state has changed. It also gives your whole app the ability to access any piece of state in any component.
In addition, there are some distinct differences between how Context and (React-)Redux pass along updates. Context has some major perf limitations - in particular, any component that consumes a context will be forced to re-render, even if it only cares about part of the context value.
So, yes, you can use them both in the same app, in the same way you can use a hammer and a screwdriver together on the same construction job.
For more details, see my posts:
Why React Context is Not a "State Management" Tool (and Why It Doesn't Replace Redux)
React, Redux, and Context Behavior
A (Mostly) Complete Guide to React Rendering Behavior
Will considering context impact the performance?
Since you want to share user preferences that (I guess) do not change often, you could use a React context to share that data.
But performance issues arise when you put multiple different data in one React context that update at different rates. This is because every component that uses the context will be rerendered even if the part of the context it is interessted in did not change. In this case you can split the context and use one context for each part of the data.
Since you want to use the context to share an application state, you should use Redux. In Redux you use selectors to select a part of the application state. This useSelector hook is implemented in a way that it only triggers a rerender of the component if the selected part changes. You can even pass it an equality function if you want to change the way state change is detected.
As Redux is already configured which internally uses the Context. So should we continue to use redux for user data.
I would say: yes, continue with Redux.
Since you already use Redux you should not spread your application state management over different concepts. Put the user settings in the Redux store (like any other application state) and don't handle them special.
Is it good practice to use Redux and Context together
Well, Redux is based on the React context. So if you use Redux it is already a good practice.
If you mean using both for application state management, I think you should go the Redux or the React context way. Mixing them makes it harder to understand where state is managed.
React 16.7 has State Hook,so I do not need react-redux anymore,is that right?
To my understanding so far, Hook API is still not fully compatible with redux, and supporting for redux is under development. There is a thread in Github for the implementation of useRedux method.
Meanwhile, I think react-redux is still a better choice at the moment, since its API is already optimised for React app's performance. Implementing your own comparing function for re-rendering logic based on updates of redux store's data is too much for small & medium size projects.
For global state still the react-redux is recommended way.
Use react-redux for disconnected components where need to access share state(global state).
Use react state for form-like components(local state)
I know that there is so many answers in this question.
Anyone explain to me how Redux help your React JS Application more flexible when you are creating a Front End Web Apps.
Thank you in Advance.
From Redux documentation:
From the very beginning, we need to stress that Redux has no relation
to React. You can write Redux apps with React, Angular, Ember, jQuery,
or vanilla JavaScript.
That said, Redux works especially well with libraries like React and
Deku because they let you describe UI as a function of state, and
Redux emits state updates in response to actions.
It's a state management library with a huge ecosystem which lets you more easily set the state for your components across whole application, manage side-effects and many more.
I recommend redux author course about redux. At later part of the course, he explains how to use it with React.
Redux is used to manage the state of the component and it supports single state management system, where as flux is a multiple state management system.
Redux uses dispatchers to dispatch the payload(data) via reducers.
If, in React, I can use connect to map state and dispatch to props, and the component I used connect on will auto-render when the Redux state (and hence props) change, why would I ever need to use subscribe?
You're talking about Redux and Redux-React (which provides the connect function, specifically for React components). Take a look at how Redux-React is implemented.
connect is just a React specific abstraction over subscribe.
What happens if you aren't using React? It's totally possible to use Redux with other frameworks or even just plain Javascript applications. In these cases, there needs to be a lower level mechanism for subscribing to changes in state.
They have also updated their documentation to speak to this regarding subscribe
It is a low-level API. Most likely, instead of using it directly, you'll use React (or other) bindings. If you commonly use the callback as a hook to react to state changes, you might want to write a custom observeStore utility. The Store is also an Observable, so you can subscribe to changes with libraries like RxJS.