<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title> New Document </title>
<meta name="Generator" content="EditPlus">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<script type="text/javascript">
/*
：
number:
string:
boolean:
null：
undefined:
：typeof
Number()、parseInt() parseFloat()
Boolean()
false：
null
undefined
""
0
null
*/
<!-- -->
var width;
var arrlist=new Date();
document.write(typeof("woanji")+"<br />"); // string
document.write(typeof(12)+"<br />"); // number
document.write(typeof(true)+"<br />"); // boolean
document.write(typeof(null)+"<br />"); // object
document.write(typeof(arrlist)+"<br />"); // object
document.write(typeof(width)+"<br />"); // undefined
function test(a,b){
alert("sum:"+(a+b));
}
// ， boolean
document.write(test instanceof Object);// true，
var sss = "123sdfg";
document.write(sss instanceof String); // false， sss string
</script>
</head>
<body>
</body>
</html>