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>