[Amphiluke]

<div style="width:50px; height: 50px; overflow:hidden;" id="container">
Длиииииииииииииииинный текст 
</div>
<p><a href="#" onclick="return isThereARoomEnough('container');">is there a room enough?</a></p>

<div style="width:50px; height: 50px; overflow:hidden;" id="container2">
Крткй текст 
</div>
<p><a href="#" onclick="return isThereARoomEnough('container2');">is there a room enough?</a></p>

<script type="text/javascript">
	function isThereARoomEnough(id) {
		var cont = document.getElementById(id);
		var clone = cont.parentNode.insertBefore(cont.cloneNode(true), cont);
		clone.style.overflow = "auto";
		var result = ((clone.scrollWidth > cont.offsetWidth) || (clone.scrollHeight > cont.offsetHeight));
		clone.parentNode.removeChild(clone);
		if (result) {
			alert("There is not enough space");
		} else {
			alert("The container is roomy enough")
		}
		return false;
	}
</script>