Introduction
React. js: It is one of the most popular JavaScript libraries for creating user interfaces, especially for single-page applications (SPAs) This is possibly very overwhelming for new React developers because there is a lot to learn. However, understanding the fundamentals can be done by breaking it down into the key concepts. In this article, we will go through the top 10 React JS concepts for beginners should know to build a React application confidently.
What is React?
Before we jump onto the meaningful definitions let’s get a glance at React. React is a JavaScript library for building fast and interactive user interfaces and is developed by none other than Facebook itself. It’s built on top of components, which you can think of as bricks of your app.
Component-Based Architecture: React enables you to split your UI into smaller, reusable components. You can add your logic and UI to each piece separately as needed, making your code scalable and easier to manage.
Declarative UI: With React, you define what you want your UI to look like, and React handles updating the DOM when your data changes.
It is used to develop both simple and highly complex apps. It is good for building responsive, dynamic, and fast UI.
Components
React is all about components. In React, everything is components — you build your component either function components or class components.
Smart-Dumb (Class) Components: Manually turned components for fine-grained control. A function component is simply a normal JavaScript function that returns JSX (an HTML-like syntax).
Class Components: These are the old way of writing components but you may still see these around. Class components are ES6 classes inherited from React. Component and should have a render() method.
As a new developer you will mostly deal with function components, but knowing class components is a plus for keeping or fixing older code bases.
JSX (JavaScript XML)
JSX: It is used for writing HTML inside JS code, which is nothing but a syntactic sugar. It helps you write React components in a more familiar and condensed way.
JSX Fundamentals: JSX is similar to HTML but is, in fact, JavaScript. For example, this JSX:
Why JSX? : It improves code readability and writability} Instead of using React to create elements. Instead of using React.createElement() to manually create elements, JSX allows you to write HTML-like code in your JavaScript files.
JSX is not HTML: JSX may look like HTML, but JSX is not HTML. In addition, there are some special rules when you write HTML in JSX, for example, class will be written as className, also self-closing tags have to be closed in JSX, etc.
Props (Properties)
Props or Properties are used to pass data from one component to another. They are component inputs, and they enable you to customize a component by passing in different values.
123 Passing Props: You pass data from a parent to a child component using props. For example:
Props are immutable: You cannot mutate props within a child component. They come from the parent and are used in order to render the UI.
Props are your key to understanding how data flows between the components of a React application.
State
Another important concept in React is state. Props are used to pass data from parent to child components, while the state is used to hold data that can change over time in a component.
State Handling: Every component can have its state. In a function component, you use the useState hook to manage the state. For example:
State Updates: The setCount function triggers a re-render with the new value of count.
The state enables you to build interactive and dynamic components that can update in response to user input or other events.
Event Handling
React allows you to manage complex interactive user components like clicks, form submissions, and keyboard events. In React, you can add event handlers to JSX elements without breaking a sweat!
Working with Events: We can attach an event handler function to a JSX element —
Event Object: React provides an event object that contains useful information about the event, and the information that provides the event object. This means that you have access to the target element, type of event, etc.
Synthetic Events: React creates a synthetic event system, which makes it consistent across browsers. It guarantees that events function uniformly on different browsers.
Handling events is the key to creating interactivity for your application and responding to user actions.
Conditional Rendering
Conditional Rendering in React You can render different content based on certain conditions. This technique is known as conditional rendering.
We can still use if-else statements in your component to decide what to render. For example:
Conditional Rendering using Ternary Operator: You can also do inline conditional rendering using a ternary operator:
Conditional Rendering: This helps us render different UI elements depending on whether a user is logged in or has filled a form or anything like that.
Lists and Keys
In React, rendering lists of items is a common task. You can use the map() method to iterate over an array and render each item as a React element.
- Rendering Lists: You can loop through an array and return a component for each item:
- Keys: Each element in a list needs a unique key prop to help React identify which items have changed, been added, or removed. This helps improve performance when updating the UI.
Keys should be unique and stable to avoid rendering issues, especially in large lists.
Component Lifecycle (Class Components)
When a component is created in its class form, React gives us special methods it calls at various points in the lifecycle of a component. This is called the component lifecycle.
componentDidMount: This method is invoked once, immediately after the component is inserted in the DOM tree. It is commonly used for fetching data or initializing third-party libraries.
componentDidUpdate: This is invoked immediately after updating occurs.
componentWillUnmount: This method is invoked right before a component is removed from the DOM, which makes it an ideal place to clean up any resources (like timers or subscriptions) that the component was using.
Although in modern React (using the hooks) lifecycle methods are represented by useEffect, knowing class component lifecycles is still useful.
Use of React Developer Tools
As a beginner, debugging your React application and accessing its state, props, and components is inevitable. One such tool that can be useful in this regard is React Developer Tools which is a browser extension.
Inspecting Components: The React Developer Tools allows you to inspect the React component tree in the application, view props and state, and even edit them to see their effect on the UI.
Performance Profiling: React Developer Tools also provides performance insights to help you understand how well your app performs and identify performance bottlenecks.
Conclusion
It can be a challenging learning experience, but once you understand the core concepts, there is the potential to build robust applications using React. By understanding these 10 beginner concepts—components, JSX, state, props, event handling, conditional rendering, lists, component lifecycle, and the use of developer tools—you will already be on your way to mastering how React works. With additional experience, you can explore more advanced topics such as hooks, context, and performance optimization. Continue learning, and before long you’ll be creating dynamic, responsive user interfaces with React!
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