12. Advanced JavaScript Utilities

These advanced techniques and utilities help you write faster, more efficient, and more maintainable JavaScript.

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12.1 Performance

Throttling

Limits how often a function runs. Useful for scroll/resize events.

function throttle(fn, delay) {
	let last = 0;
	return function(...args) {
		let now = Date.now();
		if (now - last > delay) {
			last = now;
			fn.apply(this, args);
		}
	};
}
window.addEventListener('resize', throttle(() => {
	console.log('Resized!');
}, 500));

Debouncing

Delays a function until after a pause. Great for search boxes.

function debounce(fn, delay) {
	let timeout;
	return function(...args) {
		clearTimeout(timeout);
		timeout = setTimeout(() => fn.apply(this, args), delay);
	};
}
document.getElementById('search').addEventListener('input', debounce(e => {
	console.log('Searching:', e.target.value);
}, 300));

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12.2 JSON Handling

JSON.parse() & JSON.stringify()

Convert between objects and JSON strings.

let obj = {a:1};
let str = JSON.stringify(obj); // '{"a":1}'
let parsed = JSON.parse(str); // {a:1}

Tip: Always validate JSON before parsing from untrusted sources.

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Congratulations! You’ve reached the end of JavaScript Mastery. Keep practicing and building real projects to solidify your knowledge.