Lakhveer Singh Rajput

React Terminology

🛠️ Master React Terminology: A Guide for Experienced Developers 🚀

React is a popular library for building dynamic and interactive user interfaces. But as an experienced developer, understanding its core concepts and advanced terminology is essential to excel. This blog breaks down the essential React terminologies with detailed descriptions and examples to solidify your knowledge. Plus, we’ll include tricky interview questions to help you ace those challenging interviews! Let’s get started. 🌟

💡 Essential React Terminologies with Descriptions

1. JSX (JavaScript XML)

JSX is a syntax extension for JavaScript that allows developers to write HTML-like code within JavaScript. It makes the code more readable and intuitive by closely resembling the UI structure. JSX is transpiled to React.createElement() calls under the hood.

Example:

const element = <h1>Hello, World!</h1>;
ReactDOM.render(element, document.getElementById('root'));

Why Use It? JSX makes the process of creating React components faster and easier by letting you visualize the component hierarchy directly in the code.

Interview Question: Why is JSX not mandatory in React?
Answer: JSX is syntactic sugar for React.createElement(). While it’s convenient, you can write React code without it by directly using React.createElement().

2. Virtual DOM

The Virtual DOM is a lightweight, in-memory representation of the actual DOM. React updates this Virtual DOM first, calculates the changes (a process called “diffing”), and efficiently updates the real DOM only where necessary.

Why It Matters? Manipulating the real DOM can be slow and resource-intensive. The Virtual DOM enhances performance by minimizing direct DOM manipulations.

Tricky Question: How does React differentiate between two elements in the Virtual DOM?
Answer: React uses unique keys to identify elements. These keys ensure efficient updates by helping React determine which items have changed, been added, or removed.

3. Props (Properties)

Props are immutable objects used to pass data from parent to child components. They allow you to customize a component by passing in different values.

Example:

function Greeting(props) {
  return <h1>Hello, {props.name}!</h1>;
}
<Greeting name="John" />;

Key Point: Props are read-only, meaning a child component cannot modify the props it receives.

4. State

State is a mutable object that holds data or information about the component. It determines how the component behaves and looks at any given time. React uses the useState hook (for functional components) to manage state.

Example:

function Counter() {
  const [count, setCount] = React.useState(0);
  return (
    <button onClick={() => setCount(count + 1)}>
      Clicked {count} times
    </button>
  );
}

Why It’s Important: Unlike props, state is managed within the component and can be updated dynamically based on user interactions or other events.

5. Lifecycle Methods

Lifecycle methods are hooks that allow you to run code at specific points during a component’s life (Mounting, Updating, and Unmounting).

Key Lifecycle Methods:

• componentDidMount: Runs after the component is rendered.
• componentDidUpdate: Runs after the component updates.
• componentWillUnmount: Runs before the component is removed.

For functional components, the useEffect hook is used to mimic lifecycle methods.

Example of Cleanup in Functional Components:

useEffect(() => {
  console.log("Component mounted!");

  return () => {
    console.log("Component will unmount!");
  };
}, []);

6. Context API

The Context API allows you to pass data deeply through the component tree without using props at every level. This is especially useful for global data like themes or authentication state.

Example:

const ThemeContext = React.createContext('light');

function App() {
  return (
    <ThemeContext.Provider value="dark">
      <Toolbar />
    </ThemeContext.Provider>
  );
}

function Toolbar() {
  const theme = React.useContext(ThemeContext);
  return <div style=>Toolbar</div>;
}

7. React Fragments

React Fragments let you group multiple elements without adding an extra DOM node. This helps reduce unnecessary nesting and keeps the DOM clean.

Example:

function List() {
  return (
    <>
      <li>Item 1</li>
      <li>Item 2</li>
    </>
  );
}

Why It’s Useful: Fragments are especially handy when rendering lists or returning multiple elements from a component.

🤔 Trickiest React Interview Questions and Answers

1. What is the difference between a controlled and an uncontrolled component?
   • Answer:
     • A controlled component has its state managed by React, typically using useState.
     • An uncontrolled component manages its own state in the DOM, often accessed using refs.

   Example of a Controlled Component:

   function ControlledInput() {
     const [value, setValue] = React.useState('');
     return <input value={value} onChange={(e) => setValue(e.target.value)} />;
   }
   

2. Explain Reconciliation in React.
   • Answer: Reconciliation is React’s process of updating the DOM efficiently. It compares the Virtual DOM with the previous version and updates only the parts that have changed.
3. What are Higher-Order Components (HOCs)?
   • Answer: HOCs are functions that take a component as input and return an enhanced component. They are used to add reusable logic to components.

   Example:

   function withLogger(WrappedComponent) {
     return function EnhancedComponent(props) {
       console.log("Rendering:", WrappedComponent.name);
       return <WrappedComponent {...props} />;
     };
   }
   

4. Why use React.memo()?
   • Answer: React.memo optimizes functional components by memoizing their results. It prevents unnecessary re-renders when props remain unchanged.

🎯 Final Thoughts

Understanding these React terminologies and concepts is crucial for building scalable applications and acing technical interviews. Each term we’ve covered here is a building block in React’s ecosystem. Whether you’re coding or interviewing, knowing the “why” behind these concepts will make you stand out.

💬 What’s your favorite React term or concept? Drop a comment and let us know! 🚀