[j0hnik]

<button id="btn">Кнопка</button>
		<div id="block" style="overflow:hidden; width:300px; transition:1s;">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Maxime corporis animi neque reprehenderit! Reprehenderit aliquam ea qui quae natus illo, amet, quidem, debitis eaque, dolorum ducimus. Velit, doloremque neque magnam.</div>
	<script>

	var height = getComputedStyle(block).height;
	block.style.height = '0px';
	btn.onclick = function(){
		block.style.height = getComputedStyle(block).height == '0px' ? height : '0px';
	};

	</script>

Думаю что это вам поможет