Work with legacy and simple sites using jQuery selectors, events, AJAX, effects, and plugins.
Lessons
Cache selectors and minimize DOM work.
jQuery Performance Tips is easiest to learn by reading the example, changing it, and observing the result.
// Cache the selector once instead of querying repeatedly
const $list = $('#list');
for (let i = 0; i < 5; i++) {
$list.append('<li>Item ' + i + '</li>'); // reuses cached object
}
// Chain to avoid re-selecting
$('#box').addClass('active').css('color', 'green').fadeIn();Practice the jQuery Performance Tips example in a small scratch file, then explain what changed and why.