how do I access XHR responseBody (for binary data) from Javascript in IE?

I've got a web page that uses XMLHttpRequest to download a binary resource. In Firefox and Gecko I can use responseText to get the bytes, even if the bytestream includes binary zeroes. I may need to coerce the mimetype with overrideMimeType() to make that happen. In IE, though, responseText doesn't work, because it appears to terminate at the first zero. If you read 100,000 bytes, and byte 7 is a

[rikuba]

overrideMimeType

[youpy]

overrideMimeType 代替

[shinichitomita]

overrideMimeType相当をIEで。responseBody, VBScript