A basic implementation of query string persistence using vanilla JavaScript.

• Reads and parses query string parameters from the URL.
• Stores user data (e.g., theme preference, language setting) in query string.
• Updates the URL with new query string parameters.
• Handles URL changes and applies user preferences accordingly.

Note: While query string persistence can be a convenient technique in certain situations, it also has some limitations and potential security concerns. It is generally recommended to use more robust methods, such as server-side sessions or client-side storage, for managing user state and data in modern web applications.