NextJS: The useEffect Conundrum – Why It Refreshes and Re-renders Again to Default

If you’re a NextJS developer, chances are you’ve encountered the infamous useEffect issue where it refreshes and re-renders your component again to its default state. It’s frustrating, to say the least. In this article, we’ll delve into the reasons behind this phenomenon and provide you with actionable solutions to overcome it.

What is useEffect, and Why is it Important?

useEffect is a Hook in React that allows you to run side-effects in functional components. It’s essential for handling tasks that require DOM manipulation, API calls, or setting timers. In NextJS, useEffect is used extensively for server-side rendering (SSR) and client-side rendering (CSR).

  
  import { useState, useEffect } from 'react';

  function Example() {
    const [count, setCount] = useState(0);

    useEffect(() => {
      // Run this code when the component mounts
      console.log('Component mounted!');
    }, []);

    return (
      

        
Count: {count}
         setCount(count + 1)}>Increment
      
    );
  }
  

The useEffect Refresh and Re-render Issue

When you use useEffect with an empty dependency array `[]`, it runs once when the component mounts. However, when you navigate away from the component and come back, the useEffect hook is triggered again, and your component is re-rendered to its default state. This can lead to unexpected behavior, such as:

• Loss of user input or data
• Unwanted API calls or requests
• Inconsistent state management

Why Does useEffect Refresh and Re-render?

There are several reasons why useEffect refreshes and re-renders your component:

1. Server-Side Rendering (SSR): NextJS uses SSR to pre-render pages on the server. When you navigate to a new page, the server re-renders the component, triggering useEffect again.
2. Client-Side Rendering (CSR): When the client receives the pre-rendered HTML, it rehydrates the component, causing useEffect to run once more.
3. Component Re-mounting: When you navigate away from a component and come back, NextJS re-mounts the component, triggering useEffect to run again.
4. Dependency Array: An empty dependency array `[]` tells React to run useEffect only once. However, when the component re-renders, the dependency array is re-evaluated, causing useEffect to run again.

Solutions to the useEffect Refresh and Re-render Issue

Don’t worry; we’ve got you covered! Here are some solutions to overcome the useEffect refresh and re-render issue:

1. Use a Cache

Implement a cache to store the data fetched by useEffect. This ensures that the data is not re-fetched when the component re-renders.

  
  import { useState, useEffect } from 'react';
  import { Cache } from 'next/cache';

  const cache = new Cache();

  function Example() {
    const [data, setData] = useState(null);

    useEffect(() => {
      const cachedData = cache.get('data');
      if (cachedData) {
        setData(cachedData);
      } else {
        fetchData().then((data) => {
          cache.set('data', data);
          setData(data);
        });
      }
    }, []);

    return (
      

        
Data: {data}
      
    );
  }
  

2. Use a Singleton

Create a singleton instance of your data-fetching function. This ensures that the data is fetched only once and remains consistent across component re-renders.

  
  import { useState, useEffect } from 'react';

  const singleton = {
    instance: null,
  };

  function fetchData() {
    if (!singleton.instance) {
      singleton.instance = axios.get('https://api.example.com/data');
    }
    return singleton.instance;
  }

  function Example() {
    const [data, setData] = useState(null);

    useEffect(() => {
      fetchData().then((data) => {
        setData(data);
      });
    }, []);

    return (
      

        
Data: {data}
      
    );
  }
  

3. Use a Custom Hook

Create a custom hook that handles the data-fetching and caching logic. This keeps your component code clean and decouples the logic from the component.

  
  import { useState, useEffect } from 'react';

  const useFetchData = () => {
    const [data, setData] = useState(null);
    const [loading, setLoading] = useState(false);

    useEffect(() => {
      const fetchData = async () => {
        setLoading(true);
        const response = await axios.get('https://api.example.com/data');
        setData(response.data);
        setLoading(false);
      };
      fetchData();
    }, []);

    return { data, loading };
  };

  function Example() {
    const { data, loading } = useFetchData();

    return (
      

        {loading ? (
          
Loading...
        ) : (
          
Data: {data}
        )}
      
    );
  }
  

4. Use getStaticProps or getServerSideProps

In NextJS, you can use `getStaticProps` or `getServerSideProps` to pre-render your component with the required data. This approach eliminates the need for useEffect and ensures that your component is rendered with the correct data.

  
  import { GetStaticProps } from 'next';

  function Example({ data }) {
    return (
      

        
Data: {data}
      
    );
  }

  export const getStaticProps = async () => {
    const response = await axios.get('https://api.example.com/data');
    return {
      props: {
        data: response.data,
      },
    };
  };
  

Conclusion

In conclusion, the useEffect refresh and re-render issue can be frustrating, but with the right approaches, you can overcome it. By using a cache, singleton, custom hook, or `getStaticProps`/`getServerSideProps`, you can ensure that your component behaves as expected, even when navigating away and coming back.

Remember, understanding the underlying reasons behind the useEffect refresh and re-render issue is key to finding the right solution for your use case.

Final Thoughts

If you’re still struggling with the useEffect refresh and re-render issue, don’t hesitate to reach out to the NextJS community or seek help from a seasoned developer. With patience, persistence, and the right approaches, you can overcome this hurdle and build robust, scalable, and maintainable NextJS applications.

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