Convert JavaScript to ES6+

I need help converting older JavaScript code to modern ES6+ syntax. Please update the code to use contemporary JavaScript features and best practices while maintaining its functionality. Here's the code to modernize: ```javascript [PASTE CODE HERE] ``` Please provide: 1. MODERNIZED CODE * Complete updated version using ES6+ features * Consistent, clean coding style * Proper use of modern JavaScript best practices * Preserved functionality and behavior 2. CHANGES EXPLAINED * Overview of the main updates made * Explanation of each significant syntax change * How new ES6+ features improve the code * Any performance or readability benefits 3. SPECIFIC ES6+ FEATURES APPLIED * Arrow functions * Template literals * Destructuring * Spread/rest operators * let/const declarations * Classes (if applicable) * Promises/async-await (if applicable) * Modules (if applicable) * Other relevant ES6+ features 4. ADDITIONAL IMPROVEMENTS * Modern best practices implementation * Code structure enhancements * Potential performance optimizations * Better error handling if applicable * Any security improvements 5. COMPATIBILITY CONSIDERATIONS * Browser compatibility notes * Transpilation recommendations if needed * Polyfill suggestions if applicable * Progressive enhancement strategies * How to ensure backward compatibility Please ensure the modernized code maintains exactly the same functionality as the original while leveraging modern JavaScript features for improved readability, maintainability, and performance.