JavaScript判断DIV内容是否为空的实现方法

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>如何判断DIV中的内容为空</title> 
<script type="text/javascript" src="jquery-2.2.0.js"></script> 
<script type="text/javascript"> 
$(function(){ 
$("#content").append("<div id='dv'>您好！</div>"); 
$("#btn").click(function(){ 
var content = $("#content").html(); 
var noContent = $("#no_content").html(); 
if(content == null || content.length == 0) 
{ 
alert("content:"+conten); 
} 
if(noContent == null || noContent.length == 0) 
{ 
alert("noContent:"+noContent); 
} 
}); 
}); 
</script> 
</head> 
<body> 
<div id="content"></div> 
<div id="no_content"></div> 
<input type="button" id="btn" value="判读DIV为空"/> 
</body> 
</html>