怎么用JS来取得本身页面得html源码?

Question

<script language="vbscript">
Function bytes2BSTR(vIn)
Dim strReturn,i,ThisCharCode,innerCode,Hight8,Low8,NextCharCode
strReturn = ""
For i = 1 To LenB(vIn)
ThisCharCode = AscB(MidB(vIn,i,1))
If ThisCharCode < &H80 Then
strReturn = strReturn & Chr(ThisCharCode)
Else
NextCharCode = AscB(MidB(vIn,i+1,1))
strReturn = strReturn & Chr(CLng(ThisCharCode) * &H100 + CInt(NextCharCode))
i = i + 1
End If
Next
bytes2BSTR = strReturn
End Function
</script>
<script language="javascript">
var xmlhttp= new ActiveXObject("Msxml2.xmlhttp");
xmlhttp.open("GET","http://www.baidu.com/",false);
xmlhttp.send();
document.write("<div>");
document.write(bytes2BSTR(xmlhttp.ResponseBody)); //代码.
document.write("</div>")
</script>