Microsoft jscript runtimr error:object expected

[istring]

从msdn拷了一段代码：
// Initialize an array with three elements.
var myArray = new Array("Hello", 42, new Date(2000,1,1));
print(myArray.length); // Prints 3.
// Add some expando properties. They will not change the length.
myArray.expando = "JScript";
myArray["another Expando"] = "Windows";
print(myArray.length); // Still prints 3.

然后运行cscript mytest.js的到错误object expected,谁知道啊？
【msdn上是用jsc来编译通过的】