Refused to get unsafe header "Content-Length" when communicating with the server

function funcDbGet(){
    var url = 'https://--- omitted ---';
    var req = new XMLHttpRequest();
    req.open("GET", url, true);
    req.onreadystatechange=function(){
        if(req.readyState===XMLHttpRequest.DONE){
            if(req.status===200){
                console.log("200" + req.responseText);
            }
            else{
                console.log("err" + req.status);
                console.log(req.responseText);
            }
        }
    };
    req.send(null);
}