XMLHttpRequest: Get blob file and read binary data

I'm trying to read a byte array from an Image using XMLHttpRequest:

var xhr = new XMLHttpRequest();
    xhr.responseType = "blob"; // arraybuffer
    xhr.onabort = function() {
    
    };
    xhr.onerror = function () {
        console.log( xhr.error );
    };
    xhr.onloadend = function () {
    
    };
    xhr.onloadstart = function () {
    
    };
    xhr.ontimeout = function () {
        console.log( "Request timed out after " + xhr.timeout );
    };
    xhr.onload = function () {
    
        console.log( xhr.getAllResponseHeaders () );
        console.log( xhr.metrics );
        console.log( xhr.response );
        if(xhr.response) {
            localStorage.setItem("mxm_image_arraybuffer", xhr.response);
        }
        callback(xhr.response);
    };
    /xhr.addEventListener("load", function() {
    
        console.log( "RESPONSE ");
        console.log( xhr.getAllResponseHeaders () );
        console.log( xhr.response );
    
        callback(xhr.response);
    }, false);*/
    xhr.open("GET", path, 0); //async 0, sync 1
    xhr.send(null);

I have several problems here:

I'm not sure if the responseType is "blob", since normally in JavaScript it woud be "arraybuffer"; In a ordinary JavaScript it is as simple as

var xhr = new XMLHttpRequest();
    xhr.open("GET", path, true);
    xhr.responseType = "arraybuffer";
    xhr.onload = function() {
        callback(xhr.response);
    };
    xhr.send(null);

Assumed that the closest thing to binary is blob, I make the request with that, but I cannot access this response object:

IKJSBlob

This is tvOS native object, but it seems it does not expose its implementation. For my knowledge, the native ObjC object should have a "data" property of type NSData, but I have no access to this, likely it's not a JSExport, so I cannot do anything with it.