Lastly, you’ll create a script element where you write your React code. And as you can reuse functions, so also you can reuse components, merge them and thereby creating a complex user interface. React allows developers to create complex UI from an isolated snippet of code as mentioned earlier. To understand the statement better, you need to start thinking in React Component. Once a component is declared, it can be used in other components. Program to demonstrate the use of class based components in other components. Project setup of ReactJS is explained using CDN files and also using npm packages to build the project.

React by Example Lessons

The component also requires a render() method, this method returns HTML. This section will give you an overview of how to use Class components in React. With the addition of Hooks, Function components are now almost equivalent to Class components. The differences are so minor that you will probably never need to use a Class component in React. They are passed to a component where that component is used.

React Router V6

But the problem with this approach is that you learn very little about a whole lot of things. When you go to apply your knowledge in the real world, you trip across massive holes in your knowledge and understanding. Conveniently hidden in The Fog, so you fall right in. I know from first-hand experience that you can go in knowing zero, nothing, and just get a grasp on everything as you go and start building right away. Extracting out the logic for finding individual users based on id reduces code redundancy in those cases.

React by Example Lessons

ReactJS does not allow a component to modify its own props as a rule. The only way to modify the props is to change the props being passed from the parent component to the child component. This is generally done by passing a reference to a function in the parent component, which changes the props being passed to the child component.


Each lesson in this 28-part course is a single index.html file. This keeps your focus on learning React, with no distractions.

Potentially, there could be all kinds of components that render user objects. E.g. a chat sidebar could display each user using an individual component, a friend component or modal could equally be wired up to the shared store. This file structure is used by Facebook, the creators of React, and is whatcreate-react-app automatically generates. Using this structure, a lot of set-up is abstracted away. We do not need to deal with writing the HTML document or connecting it with JavaScript, as it is always the boiler plate code withindex.html, index.js, and App.js.

The constructor only uses this.state to assign initial state, and all other methods need to use set.state() method. The constructor is a method used to initialize an object’s state in a class. It automatically called during the creation of an object in a class. Replacing componentDidMount, We use the useEffect hook with the second argument of []. The second argument of the useState hook is normally an array of a state that changes, and useEffect will be only called on these selected changes. But when it’s an empty array like this example, it will be called once on mounting.

And we’ll close out by learning how to import and export modules. React and moment are both npm packages, so what is happening here? App.jsis pulling in specific content from these two packages! You can see in the App class that Component and moment are both being used in the render()method. They are being imported from the node_modules folder. This can lead to unexpected behavior in your app if the code above is called multiple times in the same update cycle. To avoid this you can pass an updater callback function to setState instead of an object.

The Best React Examples

If we were displaying data from a database, Alexa, Ben, and Claudia’s database IDs could be used as keys. If you need to review JavaScript, we recommend reading this guide. Note that we’re also using some features from ES6 — a recent version of JavaScript.

Understanding how the data flows is very crucial to building React component. The files that describe what you are seeing in the frontend live in the src folder. Since this React tutorial focuses on the beginners, we will write all the src files from scratch. The index.html in the public folder is similar to the one we created earlier.

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We’ll want the top-level Game component to display a list of past moves. It will need access to the history to do that, so we will place the history state in the top-level Game component. We’ll now change the Square to be a function component. We have not defined the handleClick() method yet, so our code crashes. If you click a square now, you should see a red error screen saying something like “this.handleClick is not a function”. Lifting state into a parent component is common when React components are refactored — let’s take this opportunity to try it out.

React by Example Lessons

If you want to inspect and debug your application, check your components tree or see how React works in real-time, you will need this tool. It is available as a browser extension for Chrome and Firefox. You will realize that another component called TodosList has the responsibility to handle the todos list. This is where we will apply the knowledge of props earlier explained. For instance, the TodosList component will be accessing the data and display its todos items.

React Styling

Whenever an HTML document is loaded in the browser as a web page, a corresponding Document Object Model is created for that page. This is simply an object-based representation of the HTML. As a JavaScript developer, you are sure to have interacted with the real DOM while building interactive websites. Though, you may have been able to avoid understanding how it works. So, let’s reiterate to enable you to quickly grasp the concept behind virtual DOM that React provides for us. Till then, we will be creating components based on what we are viewing at the moment. If you are still finding it tough with JavaScript, just read and code along.

See Debug applications running on custom URLs below. If you created your application with create-react-app, your development environment is already preconfigured to use ESLint. IntelliJ IDEA provides code completion for React APIs and JSX in JavaScript code.

Of course having a store that simply wraps our state object isn’t too useful yet. If we update their state using setState, React re-evaluates the component’s render function and updates the rendered DOM structure.

React does not know what to do when an expression is used inside the .js file. To start with ReactJS, we need to first import the react packages as follows. Here is the working ReactJS example using cdn files and babeljs script. Facebook maintains ReactJS, the library, so it is well maintained and kept updated. The book-only version of Pure React has sold over 2,000 copies and helped so many developers like you (and me!). I taught the basics of React the same way I had pieced it together… with small steps, and lots of practice exercises. You could sit right down and start from scratch, with confidence and momentum.

By including the export line, we are allowing other files to import things from the App.js file. There are different types of exports, like named exports and default exports, but we will dive deeper into this topic in a later lesson. Create-react-app version 3.0.0 was released April 22, 2019. It makes a small change that defines App slightly differently. When you runcreate-react-app it may generate class App extends Component if you have an old version, or function App() if you have a newer version. Don’t be surprised if you see an App that looks like the code block below. Always use the setState() method to change the state object, it will ensure that the component knows its been updated and calls the render() method .

You can use the Local link to open the app in your own browser. The second is for any other computers on your network that you want to access your app from. You will find there is no predefined way to structure your app. To ensure you get the most from React, you’ll need to spend a little more time researching and implementing popular and effective ways to structure your app. Passionate about learning, creating cool stuff, and helping others achieve their career goals. Your very first React app will be a static site about React!

Using name as a prop lets us customize the Greeting component, so we can reuse that component React by Example Lessons for each of our greetings. This example also uses the Greeting component in JSX.

There is a collection of pre-defined quotes collected and store in constant. Each time new quote display to user background color will also get change. In this example process From data on real-time as user enter or select any option of given form, pass the value in URL and show the option in another section. In this example we will create Stateful component and this example gives an idea how onChange even works in React JS. This is a simple example to list Json records in tabular format.

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