How can I detect when Session Storage data is about to expire

javascript
function checkSessionStorageExpiration() {
  const storageKey = 'yourUniqueStorageKey';
  const now = new Date();
  const storedData = sessionStorage.getItem(storageKey);
  if (storedData) {
    const storedDataObject = JSON.parse(storedData);
    const expirationDate = new Date(storedDataObject.timestamp);
    if (now.getTime() > expirationDate.getTime()) {
      // Data has expired, remove it from session storage
      sessionStorage.removeItem(storageKey);
    }
  }
}

// Call the function periodically to check for expiration
setInterval(checkSessionStorageExpiration, 1000); // Check every second

This code checks if the stored data has expired by comparing the current time with the timestamp stored along with the data. If the stored data has expired, it removes the data from session storage.

Explanation

1. Get the Stored Data: Retrieve the stored data from session storage using `sessionStorage.getItem()`.
2. Parse the Stored Data: Convert the stored data from a string to a JavaScript object using `JSON.parse()`.
3. Get the Expiration Date: Extract the timestamp from the stored data object.
4. Compare with Current Time: Compare the current time with the expiration date.
5. Remove Expired Data: If the data has expired, remove it from session storage using `sessionStorage.removeItem()`.

Example Usage

Here is a sample React code snippet that demonstrates the usage of Session Storage with an expiration time:

javascript
import React, { useState, useEffect } from 'react';

function App() {
  const [data, setData] = useState(null);
  const [expiration, setExpiration] = useState(null);

  useEffect(() => {
    const storageKey = 'my-key';
    const now = new Date();
    const storedData = sessionStorage.getItem(storageKey);
    if (storedData) {
      const storedDataObject = JSON.parse(storedData);
      const expirationDate = new Date(storedDataObject.timestamp);
      if (now.getTime() > expirationDate.getTime()) {
        setData(null);
        setExpiration(null);
      } else {
        setData(storedDataObject.content);
        setExpiration(expirationDate);
      }
    } else {
      const newContent = 'New Content';
      const newExpiration = new Date(now.getTime() + 30 * 60 * 1000); // 30 minutes from now
      const newDataObject = { timestamp: newExpiration, content: newContent };
      setData(newContent);
      setExpiration(newExpiration);
      sessionStorage.setItem(storageKey, JSON.stringify(newDataObject));
    }
  }, []);

  return (
    <div>
      <h1>Data: {data}</h1>
      <h2>Expiration: {expiration.toLocaleString()}</h2>
    </div>
  );
}

export default App;

Best Practices

- Use a custom React hook: Extract the storage functionality into a reusable custom React hook to simplify usage across multiple components.
- Clear unnecessary data: Ensure to clear unnecessary data from session storage to maintain privacy and free up storage space.

By leveraging Session Storage with an expiration time effectively, you can enhance the functionality and responsiveness of your React applications while maintaining data freshness and security[1][3][5].