Better way of using callback in javascript

Hi,
Here is the code which i am using ... this includes a callback... although code seems to be working fine.. Need help from experts on its design a better way to write the same or any flaws in it  :

clock.groups.list(userId, callback);
clock.roster.listContacts(userId, callback);

var callback = function(errorThrown, data, name) {
         if(errorThrown === null) {
             if(name === 'groups.list') {
                 mygroupList = data;
             }
             else if (name === 'roster.listContacts') {
                 data.forEach(function(elem){mybuddyList.push(elem)});
             }
         }
}

exports.groups = {};
exports.groups.list = function(userId, callback) {
    callMethod('groupList', userId, callback);
}
exports.roster = {};
exports.roster.listContacts = function(userId, callback) {
    callMethod('listContacts', userId, callback);
}

callMethod = function(name, userId, callback) {
    $.ajax({
        url : endpoint,
        type: 'POST',
        contentType: 'application/json',
        headers: {
            'X-user-id': userId,
        },
        dataType: 'json',
        success: function(data, textStatus, jqXHR){
            callback(null, data, name);
        },
        error: function(jqXHR, textStatus, errorThrown) {
            callback(errorThrown, null, name);
        }
    });
}

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Thanks