Prototype - empty() 方法
此方法测试元素是否为空(即，仅包含空格)。
语法
element.empty;
返回值
如果发现元素为空，则返回 true，否则返回 false。
示例
<html>
<head>
<title>Prototype examples</title>
<script type = "text/javascript" src = "/javascript/prototype.js"></script>
<script>
function showResult() {
if($('wallet').empty() ) {
alert( "Wallet is empty " );
}
if($('cart').empty() ) {
alert( "Cart is full" );
}
}
</script>
</head>
<body>
<p>单击按钮查看结果。</p>
<div id = "wallet"> </div>
<div id = "cart">full!</div>
<br />
<input type = "button" value = "showResult" onclick = "showResult();"/>
</body>
</html>
In this example −
$('wallet').empty();
// -> true
$('cart').empty();
// -> false
prototype_element_object.html
