The Ultimate React.js Guide for Developers
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Learning JavaScript libraries and frameworks can be overwhelming. There are many libraries to choose from, and no proper step-by-step guides that’ll teach you how to use these libraries to their fullest potential.
That’s why, in this guide, you’ll learn the most popular JavaScript library, used by hundreds of thousands of developers worldwide - .
This guide covers the complete , , essential , and project ideas that you can build & deploy and put up on your portfolio and get a job.
React.js is a front-end JavaScript library for building user interfaces. It was developed by and is maintained by Facebook and the open-source community.
React.js is a phenomenal library that is easy to understand, has excellent cross-platform support, has a fantastic community, and is one of the most loved libraries out there.
There are also two great React.js competitors: , . These libraries and frameworks are mainly used to create fast and efficient .
Although these are great technologies, taking a quick look at , we can clearly see that React.js is still in the lead by far.
You might be wondering, what are the prerequisites to learn such a great JavaScript library?
There’s only one prerequisite and that is - .
Do not jump straight into React.js without understanding the topics I've mentioned below.
Before learning React, you should have a good understanding of these topics:
React JS is a component-based front-end library, which means that all parts of a web application are divided into small components.
A component is a small piece of the user interface. Every React.js application is a .
Components let you split the UI into independent, reusable parts. So when you're building an application with React, you'll build independent and reusable components, and then you'll combine them to build a full-fledged web application.
Let’s take an example to represent what React.js components are:
This website is entirely built in React.js. So imagine we're building this website. How would we make it?
Firstly, we’ll split the User Interface into small components like:
These components will then be assembled together to form the entire application.
React components allow for maximum reusability, enabling developers to write cleaner code and manage applications more efficiently.
In React, there are two types of components: and .
Let’s first look at a :
import React, { Component } from "react";
class Example extends Component {
render() {
return <div>...</div>;
}
}If you're not familiar with classes, class methods, or what the keyword means, don't worry! Class-based components are rarely used anymore.
They’ve been largely replaced by their simpler counterparts, .
Although class components were used in the past, functional components with hooks have become the standard because of their simplicity and ease of use.
Now, let's take a look at a :
import React from "react";
const Example = () => {
return <div>...</div>;
};As you can see, functional components are simpler and more concise. They allow you to build the same UI and manage the application state with hooks, making them the preferred approach in modern React development.
If you're starting with React, focus on learning and hooks for a better development experience.
That's It! This is a .
You can see how easy it is to create a React component. Here's an example:
return <div>Hello World!</div>;You might be wondering: Why are we writing HTML when returning something?
This tag syntax is neither a string nor HTML.
It is called (JavaScript XML).
JSX is a syntax extension to JavaScript. It is used in React to describe what the UI should look like. While JSX may remind you of a template language, it comes with the full power of JavaScript.
JSX produces React "elements" and forms the core syntax of React, allowing developers to define what the UI should look like with a blend of HTML-like syntax and JavaScript.
Here's an example of JSX:
return (
<div className="greetings">
<h1>Hello, {people.name}</h1>
</div>
);JSX is very similar to HTML, but there are some differences. For example:
The word is a reserved keyword in JavaScript. Since JSX is an extension of JavaScript, we use instead.
Similar to how is reserved in JavaScript, there's another reserved keyword used in HTML: the attribute in the <label> element.
In JSX, you must use the attribute as instead of .
return (
<form className="form">
<label htmlFor="name">Name</label>
<input type="text" id="name" />
</form>
);Just like , is a reserved keyword in JavaScript. To avoid conflicts, JSX uses .
In JSX, your code must return a single parent element. If you don't, the code will not compile.
You can achieve this by using either <div> elements or .
return (
<>
<h1>Welcome</h1>
<p>Thank you for joining us!</p>
</>
);React Fragments are not mandatory, but they help make the code more readable by avoiding unnecessary <div> wrappers.
Use React Fragments (<>...</>) to simplify your structure and reduce the number of unnecessary DOM elements.
In JSX, you can directly implement JavaScript expressions by using curly brackets: {...}.
This allows seamless integration of logic and dynamic content within your React components.
return (
<div>
<h1>Hello, {prop.name}</h1>
<p>{4 + 6} is ten</p>
</div>
);Unlike HTML, where you need a <script> tag or an external JavaScript file, JSX allows inline usage of JavaScript expressions directly within curly brackets.
To make our components accept different data, we use . Props are essentially arguments passed into React components. These arguments are provided via HTML attributes.
function Welcome(props) {
return <h1>Hello, {props.name}!</h1>;
}
// Using the component
<Welcome name="Adrian" />;Props are immutable, which means a component cannot change the values received through . If you need to modify data, use .
State is a plain JavaScript object used by React to represent a piece of information about the component's current situation. Think of it as the component’s memory, where it keeps track of changes over time.
import React, { useState } from "react";
function Counter() {
const [count, setCount] = useState(0); // Initializing state
return (
<div>
<p>Current count: {count}</p>
<button onClick={() => setCount(count + 1)}>Increment</button>
</div>
);
}Use the hook to manage state in functional components. It provides a way to create and update .
An is an action triggered by the user or a system-generated interaction. Examples include mouse clicks, key presses, and other user interactions.
const handleClick = () => {
console.log("Button clicked!");
};
return (
<button onClick={handleClick}>Explore More</button>
);<button onclick="handleClick()">Click</button><button onClick={handleClick}>Click</button>were introduced in React 16.8 to provide a cleaner way to use state and other React features, such as lifecycle methods, within functional components.
import React, { useState } from 'react';
const Counter = () => {
const [count, setCount] = useState(0); // Using the useState Hook
return (
<div>
<p>Count: {count}</p>
<button onClick={() => setCount(count + 1)}>Increment</button>
</div>
);
};
export default Counter;Congratulations! You’ve completed The Ultimate React.js Guide for Developers. You now have a comprehensive understanding of React.js, from the basics of to and . With this knowledge, you're ready to build powerful, interactive applications and continue growing as a React developer.
Remember, the learning doesn’t stop here. Keep building projects, exploring new features, and staying updated with the to sharpen your skills.
Happy coding, and enjoy building amazing apps with React! 🚀
