I'm a bit new to react. I see we have to import two things to get started, React and ReactDOM, can anyone explain the difference. I'm reading through the React documentation, but it doesn't say.
React and ReactDOM were only recently split into two different libraries. Prior to v0.14, all ReactDOM functionality was part of React. This may be a source of confusion, since any slightly dated documentation won't mention the React / ReactDOM distinction.
As the name implies, ReactDOM is the glue between React and the DOM. Often, you will only use it for one single thing: mounting with ReactDOM.render(). Another useful feature of ReactDOM is ReactDOM.findDOMNode() which you can use to gain direct access to a DOM element. (Something you should use sparingly in React apps, but it can be necessary.) If your app is "isomorphic", you would also use ReactDOM.renderToString() in your back-end code.
For everything else, there's React. You use React to define and create your elements, for lifecycle hooks, etc. i.e. the guts of a React application.
The reason React and ReactDOM were split into two libraries was due to the arrival of React Native. React contains functionality utilised in web and mobile apps. ReactDOM functionality is utilised only in web apps. [UPDATE: Upon further research, it's clear my ignorance of React Native is showing. Having the React package common to both web and mobile appears to be more of an aspiration than a reality right now. React Native is at present an entirely different package.]
See the blog post announcing the v0.14 release:
https://facebook.github.io/react/blog/2015/10/07/react-v0.14.html
From the React v0.14 Beta release announcement.
As we look at packages like react-native, react-art, react-canvas, and react-three, it's become clear that the beauty and essence of React has nothing to do with browsers or the DOM.
To make this more clear and to make it easier to build more environments that React can render to, we're splitting the main react package into two: react and react-dom.
Fundamentally, the idea of React has nothing to do with browsers, they just happen to be one of many targets for rendering trees of components into. The ReactDOM package has allowed the developers to remove any non-essential code from the React package and move it into a more appropriate repository.
The react package contains React.createElement, React.createClass and React.Component, React.PropTypes, React.Children, and the other helpers related to elements and component classes. We think of these as the isomorphic or universal helpers that you need to build components.
The react-dom package contains ReactDOM.render, ReactDOM.unmountComponentAtNode, and ReactDOM.findDOMNode, and in react-dom/server we have server-side rendering support with ReactDOMServer.renderToString and ReactDOMServer.renderToStaticMarkup.
These two paragraphs explain where the core API methods from v0.13 ended up.
TL;TR the react package is required to create and use components and hooks, react-dom contains react-dom/client and react-dom/server to render you app in the browser's DOM or inside a string (or a stream) on the server. With react-native you can use React to create native apps for Android and iOS.
This question has been asked almost seven years ago and a lot has changed since then.
Most of the answer are no longer correct or contains outdated information.
I'll try to give you a complete but simple answer with the most up to date information available.
React 18
In March 2022 React 18 has been released. It has brought some interesting changes in its public APIs.
Packages
react
As stated in React documentation:
React is the entry point to the React library. If you load React from a <script> tag, these top-level APIs are available on the React global.
Indeed it exposes most of the common React features to create and use components. Some of these are:
React.Component and React.PureComponent, used to create class components and function components
React.createElement(), used convert your JSX code from <Page title="Home page" />to React.createElement(Page, { title: "Home page" }, null)
React.Fragment, to return multiple elements without creating additional DOM elements (starting with React 16.2 you can also use <></> to create a fragment.
hooks, to let you use state and other React features without writing a class
Refs, Suspence and Transitions
Complete list of API exposed by the React object
react-dom, react-native and the others listed below are React renderers. They manage how a React tree turns into the underlying platform calls.
react-dom
The react-dom package provides DOM-specific methods that can be used at the top level of your app and as an escape hatch to get outside the React model if you need to.
This package is essentially a container used to expose both the client and server sub-packages from a single one. Indeed it exposes only two function:
createPortal(), used to create portals and render children outside the DOM hierarchy of the parent component
flushSync() is something you may not never have heard about and for a reason. Because it can significantly hurt performance.
Starting from React 18 these functions have been flagged as legacy, so they will be deprecated in future releases:
render()
hydrate()
findDOMNode()
unmountComponentAtNode()
If you are thinking "OMG they have deprecated the ´ReactDOM.render´ method from React", don't worry and read below.
The reason behind the deprecation is:
the opportunity to redesign the APIs we expose for rendering on the client and server. These changes allow users to continue using the old APIs in React 17 mode while they upgrade to the new APIs in React 18.
Keep in mind that if you continue to use those legacy APIs, new React 18 features will be disabled.
Complete list of API exposed by the react-dom package
react-dom/client
The react-dom/client package provides client-specific methods used for initializing an app on the client. Most of your components should not need to use this module.
The React DOM Client module exposes only two methods:
createRoot() is the new method to create a root where your app will. This the replacement for ReactDOM.render - see the example below
hydrateRoot() is the replacement for ReactDOM.hydrate, required to hydrate a server rendered application
Now the idiomatic way to render you app is using createRoot and render chained together:
import React from 'react';
import * as ReactDOM from 'react-dom/client';
ReactDOM
.createRoot(document.getElementById('root'))
.render(<h1>Hello, world!</h1>);
Or using a constant if you don't like chaining, it's just a matter of style:
import React from 'react';
import * as ReactDOM from 'react-dom/client';
const root = ReactDOM.createRoot(document.getElementById('root'))
root.render(<h1>Hello, world!</h1>);
Complete list of API exposed by the react-dom/client package
react-dom/server
The ReactDOMServer object enables you to render components to static markup. Typically, it’s used on a Node server
Using ReactDOMServer you can render React components server-side. It offers a wide range of methods to achieve this - there are dedicated functions for every environment:
renderToPipeableStream(), uses Node.js Streams
renderToNodeStream() (Deprecated), uses Node.js Streams
renderToStaticNodeStream(), uses Node.js Streams
renderToReadableStream(), uses Web Streams available in browsers, Deno, ...
Moreover, there are also render that can be used in the environments that don not support streams:
renderToString() discouraged from React 18
renderToStaticMarkup()
You can use them but they have limited Suspense support.
This is a the minimal working example to try ReactDOMServer on your own:
import React from 'react';
import * as ReactDOMServer from 'react-dom/server';
const html = ReactDOMServer.renderToString(<h1>Hello, world!</h1>);
Complete list of API exposed by the react-dom/server package
react-native
With React Native, React primitives render to native platform UI, meaning your app uses the same native platform APIs other apps do.
React Native has now a huge ecosystem itself and it is not limited to only render components.
Today is no longer recommended to install the react-native module yourself. Instead, you can use the the expo-cli to take advantage of its automation for the development of your application.
Other React renderers
These are some of the most interesting renderer available today (not dead) for React
react-canvas
react-canvas project is dead, but similar features can be found in
react-konva. Using it you can render your React components inside an HTML canvas.
react-three
react-three has been superseded by react-three-fiber. It allows you to build your three.js scene declaratively from React.
ink
ink is a React renderer for CLIs. Using it you can build your CLI output using components.
react-figma
react-figma is a React renderer for Figma. You can use React components as a source for your designs.
react-pdf
react-pdf is a React renderer for creating PDF files on the browser and server.
FAQ
Where did prop-types go?
With the release of react 15.5 the prop-types library
moved outside of React into a dedicated package.
It looks like they've separated React into react and react-dom packages, so you don't have to use the DOM-related part for projects where you'd like to use it in non-DOM-specific cases, like in here https://github.com/Flipboard/react-canvas
where they import
var React = require('react');
var ReactCanvas = require('react-canvas');
as you can see. Without react-dom.
Before v0.14 they were part of main ReactJs file, but as in some cases we may not need both, they separate them and it starts from version 0.14, that way if we need only one of them, our app gonna be smaller due to using only one of those:
var React = require('react'); /* importing react */
var ReactDOM = require('react-dom'); /* importing react-dom */
var MyComponent = React.createClass({
render: function() {
return <div>Hello World</div>;
}
});
ReactDOM.render(<MyComponent />, node);
React package contains: React.createElement, React.createClass, React.Component, React.PropTypes, React.Children
React-dom package contains: ReactDOM.render, ReactDOM.unmountComponentAtNode, ReactDOM.findDOMNode, and react-dom/server that's including: ReactDOMServer.renderToString and ReactDOMServer.renderToStaticMarkup.
To be more concise, react is for the components and react-dom is for rendering the components in the DOM. 'react-dom' acts as a glue between components and DOM. You will be using render() method of the react-dom to render components in the DOM and that's all you have to know when you are starting off with it.
The ReactDOM module exposes DOM-specific methods, while React has the core tools intended to be shared by React on different platforms (e.g. React Native).
http://facebook.github.io/react/docs/tutorial.html
React: React is a javascript library, designed for building better user interfaces.
React-DOM: React-DOM is a complimentary library to React which glues React to the browser DOM
We’re using React and whenever we use methods like render() or findDOMNode() we’re using React-DOM.
As we look at packages like react-native, react-art, react-canvas, and react-three, it's become clear that the beauty and essence of React has nothing to do with browsers or the DOM.
To make this more clear and to make it easier to build more environments that React can render to, they splitting the main react package into two: react and react-dom.
The react package holds the react source for components, state, props and all the code that is react.
The react-dom package as the name implies is the glue between React and the DOM. Often, you will only use it for one single thing: mounting your application to the index.html file with ReactDOM.render().
Why separate them?
The reason React and ReactDOM were split into two libraries was due to the arrival of React Native (A react platform for mobile development).
The react package holds the react source for components, state, props and all the code that is react.
The react-dom package as the name implies is the glue between React and the DOM. Often, you will only use it for one single thing: mounting your application to the index.html file with ReactDOM.render().
Related
I am very new to react and need to rebuild two Angular.js components within a .NET Content Management System (Kentico). I do not believe there is an opportunity to run a react app/component through npm so I have gone the other route and "add React to a website" (https://reactjs.org/docs/add-react-to-a-website.html). I'm using browserify with babelify to compile my app/component code for the browser.
I've made some decent progress but believe I like the flexibility functional components bring to the table where I don't find coding within a class component all that familiar. Because I'm "adding React to a site" instead of running it through npm, I BELIEVE I have no opportunity to import hooks and thus: no opportunity for useState within functional components.
Can anyone verify this for me? That indeed, "adding react to a site" precludes one from using functional components: class components are the best I can do?
I guess it boils down to: I do not believe I can import useState/useEffect when I am "adding react to a site" in a way where react and react-dom are just script references at the base of my component.
Maybe someone can verify that for me or else point out how I would capitalize on functional components/hooks?
You can use hooks and classes freely no matter how you include them. It's not relevant. The old react docs only use classes which is confusing. Try beta docs: https://beta.reactjs.org/
All,
I have an issue while doing Dynamic import of React Library (Built using webpack) in to React Application (Built using react-scripts). I was unable to import the component with normal import statements. I have tried to add the Library instance to window object and use it in react application which is working fine, but limited to Class based Components. If I try to use Functional Components, it says
`Invalid Hook Call Warning
You are probably here because you got the following error message:
Hooks can only be called inside the body of a function component.
There are three common reasons you might be seeing it:
You might have mismatching versions of React and React DOM.
You might be breaking the Rules of Hooks.
You might have more than one copy of React in the same app.`
Can anyone help on resolving my issue?
Are React, ReactJS and React.js different names for the same thing?
If they are different, what are the differences?
React = react = react.js = reactjs = ...
They all refer to the same JS library.
As Mentioned in their website:
React is a JavaScript library for building user interfaces
From what I know, .js and JS suffixes are a common thing in JavaScript world. Since React is a general world, sometimes they call it ReactJS to show it's a JS library.
Other examples are Next.js, Editor.js, Express.js, Node.js and so on...
Also you can see the website is reactjs.org, but it's called React in the page.
React is a utility package for UI implementation build by javascript.
So the base name is "react", but you can express its language more specifically by attaching js to it and make it bound to the web.
Also, it makes it distinguishable from other libraries called ReactNative.
There is no package such as react.js or ReactJs on npm and the main package is the "react" itself.
These named you've mentioned, might be for the focus on the core name itself, preventing collision from other packages with react itself
There is reactphph but the react keyword is using as a reference to this react not react in any other language or something.
How to merge node_module, project dependencies, of both Svelte and ReactJs?
I've seen guides showing how to include ReactJS file into a Svelte app
<SvelteComponent this={First} {...this.props}/>
That produces the following error:
Constructor is not a Constructor error
here is an example of including a svelte component in react. It been written by Rich Harris author of svelte:
https://github.com/Rich-Harris/react-svelte
Svelte and React are not compatible to import and use the other framework component directly.
It is definitely possible to create a Svelte app inside of a React app or vice-versa though.
You would have to instantiate the app like normal inside of the other app. The Svelte docs show how you can bind a Svelte app to a DOM node, which you can include in a React component. Make sure you also add the DOM node inside of that component, such as <div id="svelte-app" />.
I have noticed that some of the places in articles they have used React.render() and some of the places ReactDOM.render(). Is there any specific difference between these two?
This is a very recent change introduced with 0.14. They split up React into a core library and the DOM adapter. Rendering is now done via ReactDOM.render.
https://facebook.github.io/react/blog/2015/10/07/react-v0.14.html
React.render has been deprecated as of React 0.14. With packages like react-native, react-art, react-canvas, and react-three, it is clear that the beauty and essence of React has nothing to do with browsers or the DOM.
To make this more clear and to make it easier to build more environments that React can render to, the main react package has been split into two: react and react-dom.
This paves the way to writing components that can be shared between the web version of React and React Native.
The react package contains React.createElement, .createClass, .Component, .PropTypes, .Children, and the other helpers related to elements and component classes. Think of these as the isomorphic or universal helpers that you need to build components.
The react-dom package has ReactDOM.render, .unmountComponentAtNode, and .findDOMNode.
React.render has been deprecated since React 0.14. React diverged into two separate libraries. The core library knows how to work with React components, nest them together and so on, but to take the component and render it to the DOM is a separate library called ReactDOM. So to render a component, you don't use React you use ReactDOM.
import React from 'react';
import ReactDOM from 'react-dom';
Then you would apply it like so:
ReactDOM.render(App);
If you try to run it like that, back then you would probably have gotten an error that says:
Invalid component element. Instead of passing a component class, make sure to instantiate it by passing it to React.createElement.
If you get that error, it's a bit cryptic, think of the following function below is creating an instance of a component to the DOM:
const App = function() {
return <div>Howdy!</div>;
}
I passed App as a class to ReactDOM.render() and not an instance of the component. So it's saying please ensure you make an instance of the component and then pass it, or we need to instantiate it and then pass it to the DOM.
So you would fix it by passing an instance like so:
ReactDOM.render(<App />);
So that would create an instance of App and pass it to ReactDOM.render() but you would not be quite there yet as you would probably have gotten the following error message:
Target container is not a DOM element.
So React is saying I am trying to render this but I don't know where to render it to because ReactDOM takes a second argument which is a reference to an existing DOM node on the page. When you render this <App /> component, insert that HTML into this element that already exists in our HTML document. You would go to your index.html file and find the div with class="container" or whatever it is and that is the root node. All we have to do is pass a reference to that container like so:
ReactDOM.render(<App />, document.querySelector('.container'));
Then you will get the component rendering to the screen. And lastly, five years ago we got ES6 syntax so that App component from above could be rewritten like so:
const App = () => {
return <div>Howdy!</div>;
}
So using a fat arrow like that is identical to using the function keyword.