JavaScript动态调整TextArea高度的代码

<script language="javascript" type="text/javascript"> 
function adjustObjHeight(obj, defaultHeight) { 
if(obj.scrollHeight > defaultHeight) { 
obj.style.height = obj.scrollHeight + 'px'; 
} else { 
obj.style.height = defaultHeight + 'px'; 
} 
} 
window.onload = function() { 
var obj = document.getElementsByTagName('textarea'); 
var len = obj.length; 
for(var i = 0; i<len; i++) 
adjustObjHeight(obj[i], 50); 
} 
</script>

<textarea id="content" onkeyup="adjustObjHeight(this, 50);"></textarea>