Advanced JavaScript

// Prototypes & this Binding
// Prototypal inheritance
const animal = { speak() { return `${this.name} makes a sound`; } };
const dog = Object.create(animal);
dog.name = "Rex";
dog.speak(); // "Rex makes a sound"

// 'this' binding rules (in priority order):
// 1. new — creates new object
// 2. explicit — call/apply/bind
// 3. implicit — object.method()
// 4. default — global (or undefined in strict mode)

class EventEmitter {
  constructor() { this.listeners = new Map(); }
  on(event, fn) {
    if (!this.listeners.has(event)) this.listeners.set(event, []);
    this.listeners.get(event).push(fn);
  }
  emit(event, ...args) {
    this.listeners.get(event)?.forEach(fn => fn(...args));
  }
}

// Performance Utilities
// Debounce — wait until user stops typing
function debounce(fn, delay) {
  let timer;
  return (...args) => {
    clearTimeout(timer);
    timer = setTimeout(() => fn(...args), delay);
  };
}
const search = debounce(query => fetchResults(query), 300);

// Throttle — limit to once per interval
function throttle(fn, limit) {
  let inThrottle = false;
  return (...args) => {
    if (!inThrottle) {
      fn(...args);
      inThrottle = true;
      setTimeout(() => (inThrottle = false), limit);
    }
  };
}
const handleScroll = throttle(updatePosition, 100);

// ES Modules
// Named exports
export const PI = 3.14;
export function add(a, b) { return a + b; }

// Default export
export default class Calculator { }

// Import
// import Calculator, { PI, add } from './math.js';