Web API request to refresh Rollup field Dynamic 365 through JavaScript

The following JS function is used to refresh Rollup field through webapi fom javascript

function calcRollupField(serverURL,strTargetEntitySetName, strTargetRecordId, strTargetFieldName)
{
    strTargetRecordId = strTargetRecordId.replace("{", "").replace("}", "");
    var req = new XMLHttpRequest();
    req.open("GET", serverURL + "/api/data/v9.0/" +
        "CalculateRollupField(Target=@p1,FieldName=@p2)?" +
        "@p1={'@odata.id':'" + strTargetEntitySetName + "(" + strTargetRecordId + ")'}&" +
        "@p2='" + strTargetFieldName + "'", false);
    req.setRequestHeader("OData-Version", "4.0");
    req.setRequestHeader("OData-MaxVersion", "4.0");
    req.onreadystatechange = function () {
        if (req.readyState === 4) {
            req.onreadystatechange = null;
            if (req.status === 200) {
                var results = JSON.parse(this.response);
            }
            else {
                Xrm.Utility.alertDialog(this.statusText);
            }
        }
    };
    req.send(JSON.stringify({}));
}