To get right binary response we must use overrideMimeType method of XHR in beforeSend filter method of jQuery ajax call.

expect_binary.js

        $.ajax({
            type:   "POST",
            url:    href,
            beforeSend: function (xhr) {
                xhr.overrideMimeType("text/plain; charset=x-user-defined");
            },
            success: function(response) {
                var binary = Array.prototype.map.call(response, function(c) { return c.charCodeAt(0) & 0xFF; });
                console.debug('ajax done: ', binary);
            },  
            error: function(result) {
                console.debug('ajax failed: ', result);
            } 
        });