React Higher-Order Components (HOC)

As your React application grows, you may notice that multiple components share similar logic — such as fetching data, handling permissions, or managing state.

Instead of duplicating that logic across components, React provides a powerful pattern called a Higher-Order Component (HOC).

What is a Higher-Order Component?

A Higher-Order Component (HOC) is an advanced React pattern that allows you to reuse component logic by wrapping one component with another.

In simple terms:

A HOC is a function that takes a component as input and returns a new enhanced component.

Syntax:

const EnhancedComponent = higherOrderComponent(WrappedComponent);

• WrappedComponent – The original component you want to enhance.
• higherOrderComponent – A function that adds extra logic or behavior.
• EnhancedComponent – The new component that includes both original and extra functionality.

Example 1: Basic HOC Example

Let’s say you want multiple components to display loading states before showing content.

Instead of repeating loading logic in every component, you can create a reusable HOC.

import React from "react";

function withLoading(Component) {
  return function EnhancedComponent({ isLoading, ...props }) {
    if (isLoading) {
      return <h3>Loading...</h3>;
    }
    return <Component {...props} />;
  };
}

Now you can use this HOC to wrap any component:

function UserList({ users }) {
  return (
    <ul>
      {users.map((user) => (
        <li key={user}>{user}</li>
      ))}
    </ul>
  );
}

const UserListWithLoading = withLoading(UserList);

// Usage
function App() {
  const users = ["Alice", "Bob", "Charlie"];
  return <UserListWithLoading isLoading={false} users={users} />;
}

export default App;

What’s happening:

• withLoading() adds conditional rendering logic.
• The wrapped component (UserList) focuses only on displaying data.
• Logic (loading) is separated and reusable across different components.

Example 2: HOC for Data Fetching

You can also create a HOC that fetches data and injects it as props.

import React, { useEffect, useState } from "react";

function withDataFetching(WrappedComponent, url) {
  return function EnhancedComponent(props) {
    const [data, setData] = useState([]);
    const [loading, setLoading] = useState(true);

    useEffect(() => {
      fetch(url)
        .then((response) => response.json())
        .then((result) => {
          setData(result);
          setLoading(false);
        });
    }, [url]);

    return <WrappedComponent data={data} loading={loading} {...props} />;
  };
}

Use it like this:

function PostList({ data, loading }) {
  if (loading) return <p>Loading posts...</p>;
  return (
    <ul>
      {data.slice(0, 5).map((post) => (
        <li key={post.id}>{post.title}</li>
      ))}
    </ul>
  );
}

const PostsWithData = withDataFetching(PostList, "<https://jsonplaceholder.typicode.com/posts>");

function App() {
  return (
    <div>
      <h2>Posts</h2>
      <PostsWithData />
    </div>
  );
}

export default App;

Benefits:

• The PostList component focuses only on rendering UI.
• Data fetching logic lives in one reusable HOC.
• You can reuse withDataFetching for any component that needs to fetch data.

Why Use Higher-Order Components?

HOCs are ideal for:

1. Reusing logic across multiple components
2. Code separation and cleaner architecture
3. Enhancing existing components without modifying them
4. Conditional rendering and permission handling
5. Connecting components to global data sources (like Redux or APIs)

Real-World Examples of HOCs

Some popular libraries use HOCs:

• React Redux → connect() function
• React Router → withRouter() (deprecated in v6, but widely known)
• Recompose → Utility HOCs for handling state and props

Summary Table

Concept	Description
Definition	A function that takes a component and returns a new enhanced component
Purpose	To reuse logic and behaviors across multiple components
Common Use Cases	Loading states, data fetching, authentication, analytics
Modern Alternative	React Hooks (custom hooks are simpler for logic reuse)