How to deal with life cycle and state management when page refresh is handled in React projects?

React application: page refresh and life cycle, state management

In React applications, especially when using the useEffect hook, it is crucial to understand the impact of page refresh on life cycle and state management. This article will explore common problems in app.tsx and provide solutions.

Suppose app.tsx contains the following code:

 useEffect(() => {
  initAllState();
}, []);

This raises two key questions:

1. When the page is refreshed, is the code in useEffect executed every time? Is refreshing a page equivalent to reloading the app?
2. How to make sure that initAllState is executed only once (e.g., avoid duplicate network requests)?

Let's answer separately:

1. Page refresh and useEffect execute

Yes, every time the page is refreshed, the code in useEffect executes. Page refresh clears all page content in the browser and reloads all JavaScript resources. Therefore, the useEffect hook (the empty dependency array [] means that it is executed only once when the component is mounted, but refresh is also considered to be one mount) will be executed again.

Page refresh is essentially reloading the entire app, all states are reset, and the lifecycle method is rerun.

2. initAllState single execution

To ensure that initAllState is executed only once, you can use flags inside the function:

 let isInitialized = false;

function initAllState() {
  if (!isInitialized) {
    // Initialization logic (such as network request)
    isInitialized = true;
  }
}

In this way, no matter how many times useEffect is executed, the initialization logic of initAllState will only be executed on the first call. This effectively avoids duplicate network requests and unnecessary resource consumption. Another way is to use useRef to manage state:

 const isInitializedRef = useRef(false);

useEffect(() => {
  if (!isInitializedRef.current) {
    initAllState();
    isInitializedRef.current = true;
  }
}, []);

useRef provides a way to persist state between function calls, avoiding the problems that closure variables may bring, and is more reliable in more complex scenarios. Through the above method, we can ensure that the initAllState function is executed only once, thereby optimizing application performance.

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