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测试文件名为
demo.htm
<script type="text/javascript">
var a = new window.ActiveXObject('Microsoft.XMLHTTP');
a.open('get', 'demo.htm', false);
a.send(null);
alert(typeof a.responseBody); //unknown
</script>
<script type="text/javascript">
var a = function () {};
var b = function () {};
b.prototype = new a;
var c = new b;
var d = new a;
alert(c instanceof a); //true
alert(d instanceof a); //true
alert(a instanceof Function); //true
alert({} instanceof Function); //false
a.prototype = {}; //改变原型链
alert(c instanceof a); //false
alert(d instanceof a); //false
</script>
<script>
var str=new String("hello");
alert(typeof(str));//返回string(无论引用什么类型都返回的是object)
alert(str instanceof String);//返回true,明确对象特定类型
</script>
function Student(name,age){
this.name=name;
this.age=age;
}
function Man(name,age){
this.name=name;
this.age=age;
}
var stu=new Student("dc",24);
var man1=new Man("mm",34);
alert (stu instanceof Student); //返回true
alert(man1 instanceof Student); //返回false
alert(man1 instanceof Man); //返回true
alert (typeof(stu)); //返回object
alert(typeof(man1)); //返回 object