Building Your Learning Module...
Getting things ready for you!
Find videos you like?
Save to resource drawer for future reference!
Think of it as a security camera for your webpage! It watches the DOM (your webpage structure) and notifies you whenever something changes - when elements are added, removed, or their attributes change. No more constant checking!
Set timers to check every 100ms → Waste CPU checking even when nothing changes → Slow & inefficient 😰
Mutation Observer watches → Only notifies when DOM actually changes → Fast & efficient! 🚀
Elements added or removed
Class, id, style changes
Text content modified
// Create observer
const observer = new MutationObserver((mutations) => {
mutations.forEach(mutation => {
if (mutation.type === 'childList') {
console.log('Children changed!');
console.log('Added:', mutation.addedNodes);
console.log('Removed:', mutation.removedNodes);
}
});
});
// Start watching a container
const container = document.getElementById('container');
observer.observe(container, {
childList: true // Watch for children changes
});
// Stop watching when done
// observer.disconnect();| Option | What It Does | Example |
|---|---|---|
childList | Watch for added/removed children | true |
attributes | Watch for attribute changes | true |
characterData | Watch for text content changes | true |
subtree | Watch all descendants too | true |
attributeOldValue | Save previous attribute value | true |
Detect when new notifications are added to the page
React to dark mode toggles or theme switches
Track dynamic content changes for analytics
Monitor and modify page content dynamically
Always call observer.disconnect() to prevent memory leaks!
Only watch what you need - watching everything can impact performance!
Mutations are batched - you might get multiple changes at once!
Don't modify the DOM you're watching inside the callback - it'll trigger itself!
attributeFilter to watch specific attributes only (like ['class', 'style']) instead of all attributes!Watches the DOM and notifies you when it changes
Children added/removed, attributes, text changes
Better than timers - efficient & only fires when needed!
Extensions, notifications, theme changes, analytics