Set Accepts in HTTP Request to window.open javascript call [duplicate]

I have a window.open command like this:

window.open("http://MyServer/MyPage");

And I know that I can set accepts of a request, using something like this:

var client = new XMLHttpRequest();
client.open("GET", "http://MyServer/MyPage");
client.setRequestHeader("Accept", "ContentTypeName");
client.send();

Now I need to combine this two things. But I don't know how. So...

How can I set accepts in HTTP header to a call executed by a window.open command?

UPDATED
Here is a very similar question to that: window.open with headers.
And is already answered.

But as the answer suggests I write in my new window, will be not possible if my content type is a binary like:

• application/pdf
• application/vnd.ms-excel
• application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

That for my needs these types will be present. So anyone know how I can do it?