use a previously initialized CORS XHR object to POST a JSON payload

postCorsRequest.js

function postCorsRequest(theUrl, theJsonObj, theOnLoadCallback, theErrorCallback) {
    var aJsonStr = JSON.stringify(theJsonObj);
    
    var aRequest = createCorsRequest("post", theUrl);
    
    if (aRequest) {
        aRequest.onload = theOnLoadCallback;
        aRequest.onerror = theErrorCallback;
        aRequest.send(aJsonStr);
    }
}