ldapAddUserToGroup.js

function addToGroup(client, dn) {
  var groupDn = "CN=MyGroup,OU=groups,DC=mydomain,DC=com";
  var change = new ldap.Change({
    operation: 'add',
    modification: {
      member: [dn]
    }
  });

  client.modify(groupDn, change, function(err, res) {
    if (err) {
      console.error("Looks like group add FAILED: %j", err);
    } else {
      console.log("Looks like group add WORKED: %j", res);
    }
  });
}