Send Blob over POST http request with string values - post

Question

Hi I am trying to do a http POST request to send some blob data. But I also need to send some string values with it for authentication (jwt).
let options = {uname: user.uname, authKey: user.authKey, video: qde.debrief.blob}
let xhr = await xhrRequest(`${serverIp}/api/file`, "POST", options, 'none');
prom.push(xhr);
And the xhrRequest method is
//xhr function with url input and isValid and data output
function xhrRequest(url, type, body, header) {
return new Promise((resolve, reject) => {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
if (xhr.readyState === 4 && xhr.status === 200) {
resolve({ error: false, body: JSON.parse(xhr.response) });
} else if (xhr.readyState === 4 && xhr.status !== 200) {
resolve({ error: true, body: JSON.parse(xhr.response) });
}
}
xhr.timeout = 5000;
xhr.ontimeout = () => {
resolve({ error: true, body: "Error Connecting to server" });
}
xhr.onerror = function () {
resolve({ error: true, body: "Error Connecting to server" });
}
xhr.open(type, url, true);
if (type == "POST") {
if(!header){
xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
}
xhr.send(body)
} else {
xhr.send();
}
})
}