constructor始终指向创建当前对象的构造函数

        <script type="text/javascript">
var arr = [1, 56, 34, 12]; 
console.log(arr.constructor === Array); 
Foo =  function() { }; 
console.log(Foo.constructor === Function); 
var obj = new Foo(); 
//alert(obj);
console.log(obj.constructor === Foo); 
console.log(obj.constructor.constructor === Function); 
    </script>