P22 - Mastering filter() Polyfills : from Scratch
💡 Key Takeaways
✅ What is a Polyfill?
Understand how polyfills help you bring modern JavaScript features to older environments that don't support them.
✅ Why Create Polyfills?
Learn why writing your own polyfill is crucial for deep understanding and backward compatibility.
✅ How filter() Works Under the Hood
Break down the core logic of Array.prototype.filter() — how it iterates, checks conditions, and builds a new array.
✅ Write Your Own filter() Polyfill
Hands-on implementation of a working filter() polyfill in plain JavaScript.
✅ Learn thisArg usage
Explore how thisArg helps define this context inside your callback function.
✅ Edge Case Handling
Understand checks like typeof callback, this == null, and how sparse arrays are handled.