Explain Deduping?

Deduping in React usually refers to preventing unnecessary duplicate API calls or rendering when using hooks. Let's say you have a functional component that makes an API request and renders some data. In order to avoid redundant API calls, we can use the useEffect and useState hooks alongside a custom hook.

Here's an example:

import React, { useState, useEffect } from 'react';
 
// Custom hook for fetching data
const useFetchData = (url) => {
  const [data, setData] = useState(null);
  const [isLoading, setLoading] = useState(true);
  
  useEffect(() => {
    (async () => {
      try {
        const response = await fetch(url);
        const result = await response.json();
        setData(result);
      } catch (error) {
        console.error('Error fetching data:', error);
      } finally {
        setLoading(false);
      }
    })();
  }, [url]);
 
  return { data, isLoading };
};
 
const MyComponent = () => {
  const url = 'https://api.example.com/data';
  const { data, isLoading } = useFetchData(url);
 
  if (isLoading) {
    return <div>Loading...</div>;
  }
 
  return (
    <div>
      {data.map((item) => (
        <div key={item.id}>{item.name}</div>
      ))}
    </div>
  );
};
 
export default MyComponent;

In this example, we create a custom hook called useFetchData. This hook takes a single argument, the URL, and returns an object with two properties: data and isLoading.

Inside the custom hook, we have two useState hooks:

• data initially set to null
• isLoading initially set to true

We use the useEffect hook to fetch data asynchronously. This hook has url as a dependency, so it will re-run whenever the url changes.

We then use this custom hook in our MyComponent functional component. The hook manages the data fetching process and ensures deduping by preventing duplicate requests to the same URL. Even if the component re-renders or new props are received, the custom hook takes care of avoiding unnecessary API calls.

In this scenario, deduping means avoiding redundant fetches and ensuring that we only make an API request when necessary (e.g. when the url prop changes).