alert('b' in arr); alert(2 in arr); ？？？？
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>new Boolean()</title>
</head>
<body>
<script type="text/javascript">
var arr=['1','b','c'];
alert('b' in arr);
alert(2 in arr);
var obj={
a:3,
b:function(){(b=4)}
};
alert("b" in obj);
</script>
</body>
</html>
