A possible nodejs error handling convention

gistfile1.js

/* In api.js */
 
/** 
 * @param callback {function(err)}
 * 
 * err.type in { 'malformed', 'forbidden', 'service_unavailable' }
 */

exports.connect = function (callback) {
  var err = new Error('Service Unavailable, try again');
  err.type = 'service_unavailable';
  callback(err);
};


/* In client.js */

var api = require('./api');
 
api.connect(function (err) {
  if (err instanceof Error) {
    switch(err.type) {
      case 'malformed':
        // handle malformed requests
        break;
      case 'forbidden':
        // handle forbidden requests
        break;
      case 'service_unavailable':
        // handle service unavailable
        break;
      default:
        // handle this case
    }
  }
 });