js经典实例----进度条特效

HTML

<div class="main">
			<div class="container" id="container"></div>
		</div>
		<button class='btn' id="btn">start</button>

Javascript

document.getElementById('btn').addEventListener('click', function() {
				start = 0;
				sobj = setInterval(function() {
					start += 1;
					if (start >= 80) {
						clearInterval(sobj)
					};
					container.style.width = `${start}%`
				}, 100)
			})