function rpost(url, content_type, body) {
    let xhr = new XMLHttpRequest();
    xhr.open('POST', url, false);
    xhr.setRequestHeader('content-type', content_type);
    xhr.send(body);
    return xhr.responseText;
}

function add_bookmark(id, tags, isPrivate) {
    let token = '',
    data = rpost('/ajax/illusts/bookmarks/add',
                'application/json;charset=utf-8',
                JSON.stringify({ comment: "", illust_id: id, restrict: isPrivate, tags: tags })
           );
    new_win.console.log('RES: ' + data);
}

//add_bookmark('00000000', ['simple','text'], false);