Week 9

Key Concepts

• AJAX: Asynchronous JavaScript And XML — sending HTTP requests from code
• fetch(): Modern API for HTTP requests, returns a Promise
• Promises: .then() chaining, response.json(), .catch() for errors
• async/await: ES2017 syntax for synchronous-style Promise handling
• useEffect: Hook for side effects after render; empty [] runs once on mount
• Firebase: Web backend solution — hosting, databases, authentication
• Realtime Database: Single JSON object in the cloud with concurrent access
• onValue(): Real-time listener that fires on data changes, returns unregister function
• set() / push(): set() replaces value, push() adds with auto-generated key