Chapter 10 of 12

10.1 Memory Management & Garbage Collection

Engine garbage collectors allocate and automatically free memory using algorithms like Mark-and-Sweep. Memory leaks happen when unused objects remain reachable in the root reference tree.

Common Memory Leak Causes

1. Accidental Global Variables (attaching to window/globalThis) 2. Uncleared Timers (setInterval retaining closed variables) 3. Detached DOM Nodes (storing DOM references in arrays after removal) 4. Forgotten Event Listeners

10.2 Performance Optimization: Debounce vs Throttle

Debounce and Throttle Implementationjavascript

// Debounce: Delays execution until user stops triggering event for N ms
function debounce(fn, delay) {
  let timer;
  return function(...args) {
    clearTimeout(timer);
    timer = setTimeout(() => fn.apply(this, args), delay);
  };
}

// Throttle: Guarantees execution at most once every N ms
function throttle(fn, limit) {
  let inThrottle;
  return function(...args) {
    if (!inThrottle) {
      fn.apply(this, args);
      inThrottle = true;
      setTimeout(() => inThrottle = false, limit);
    }
  };
}

10.3 Web Security Best Practices

Always sanitize untrusted user inputs to prevent Cross-Site Scripting (XSS). Never use innerHTML with raw input; use textContent or DOMPurify.

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