How to use the loopback.errorHandler function in loopback

/*
 * 4. Setup error handling strategy
 */

/*
 * EXTENSION POINT
 * Add your custom error reporting middleware here
 * Example:
 *   app.use(function(err, req, resp, next) {
 *     console.log(req.url, ' failed: ', err.stack);
 *     next(err);
 *   });
 */

// The ultimate error handler.
app.use(loopback.errorHandler());


/*
 * 5. Add a basic application status route at the root `/`.
 *
 * (remove this to handle `/` on your own)
 */

app.get('/', loopback.status());

/*
 * 6. Enable access control and token based authentication.
 */

var swaggerRemote = app.remotes().exports.swagger;
if (swaggerRemote) {

var auth = oauth2.authenticate({session: false, scope: ['web', 'demo']});
app.middleware('auth:before', ['/protected', '/api', '/me', '/_internal'],
  auth);


//setting up proxy middleware
var proxy = require('./middleware/proxy');
var proxyOptions = require('./middleware/proxy/config.json');
app.middleware('routes:after', proxy(proxyOptions));


// that will be handled later down the chain.
app.middleware('final', loopback.urlNotFound());

// The ultimate error handler.
app.middleware('final', loopback.errorHandler());


app.start = function() {
  // start the web server
  return app.listen(function() {
    app.emit('started');
    console.log('Web server listening at: %s', app.get('url'));
  });
};




if (require.main === module) {
  app.start();
}

});

// -- Mount static files here--
// All static middleware should be registered at the end, as all requests
// passing the static middleware are hitting the file system
// Example:
var path = require('path');
app.use(loopback.static(path.resolve(__dirname, '../client')));

// Requests that get this far won't be handled
// by any middleware. Convert them into a 404 error
// that will be handled later down the chain.
app.use(loopback.urlNotFound());

// The ultimate error handler.
app.use(loopback.errorHandler());

app.start = function() {
  // start the web server
  return app.listen(function() {
    app.emit('started');
    console.log('Web server listening at: %s', app.get('url'));
  });
};

// start the server if `$ node server.js`
if (require.main === module) {
  app.start();
}

});

// -- Mount static files here--
// All static middleware should be registered at the end, as all requests
// passing the static middleware are hitting the file system
// Example:
var path = require('path');
app.use(loopback.static(path.resolve(__dirname, '../client/www')));

// Requests that get this far won't be handled
// by any middleware. Convert them into a 404 error
// that will be handled later down the chain.
app.use(loopback.urlNotFound());

// The ultimate error handler.
app.use(loopback.errorHandler());

app.start = function() {
  // start the web server
  return app.listen(function() {
    app.emit('started');
    console.log('Web server listening at: %s', app.get('url'));

    app.models.user.create({
      email: 'foo@bar.com',
      password: '123456',
      name: {givenName: 'Joseph', familyName: 'Toblerone'}
    });

    app.models.Animal.create({
      species:'Dog'
    })

/*
 * 4. Setup error handling strategy
 */

/*
 * EXTENSION POINT
 * Add your custom error reporting middleware here
 * Example:
 *   app.use(function(err, req, resp, next) {
 *     console.log(req.url, ' failed: ', err.stack);
 *     next(err);
 *   });
 */

// The ultimate error handler.
app.use(loopback.errorHandler());

/*
 * 6. Enable access control and token based authentication.
 */

var swaggerRemote = app.remotes().exports.swagger;
if (swaggerRemote) swaggerRemote.requireToken = false;

app.enableAuth();

/*
 * 7. Optionally start the server
 *
 * (only if this module is the main module)
 */

/*
 * 4. Setup error handling strategy
 */

/*
 * EXTENSION POINT
 * Add your custom error reporting middleware here
 * Example:
 *   app.use(function(err, req, resp, next) {
 *     console.log(req.url, ' failed: ', err.stack);
 *     next(err);
 *   });
 */

// The ultimate error handler.
app.use(loopback.errorHandler());


/*
 * 5. Add a basic application status route at the root `/`.
 *
 * (remove this to handle `/` on your own)
 */

app.get('/', loopback.status());

/*
 * 6. Enable access control and token based authentication.
 */

var swaggerRemote = app.remotes().exports.swagger;
if (swaggerRemote) swaggerRemote.requireToken = false;

/*
 * 4. Setup error handling strategy
 */

/*
 * EXTENSION POINT
 * Add your custom error reporting middleware here
 * Example:
 *   app.use(function(err, req, resp, next) {
 *     console.log(req.url, ' failed: ', err.stack);
 *     next(err);
 *   });
 */

// The ultimate error handler.
app.use(loopback.errorHandler());


/*
 * 5. Add a basic application status route at the root `/`.
 *
 * (remove this to handle `/` on your own)
 */

app.get('/', loopback.status());

/*
 * 6. Enable access control and token based authentication.
 */

var swaggerRemote = app.remotes().exports.swagger;
if (swaggerRemote) swaggerRemote.requireToken = false;

app.use(app.get('restApiRoot'), loopback.rest());
// API explorer (if present)
  try {
    var explorer = require('loopback-explorer')(app);
    app.use('/explorer', explorer);
    app.once('started', function (baseUrl) {
      console.log('Browse your REST API at %s%s', baseUrl, explorer.route);
    });
  } catch (e) {
    console.log(
      'Run `npm install loopback-explorer` to enable the LoopBack explorer'
    );
  }

  app.use(loopback.urlNotFound());
  app.use(loopback.errorHandler());

  if (require.main === module) {
    app.start();
  }

});

/*
 * 4. Setup error handling strategy
 */

/*
 * EXTENSION POINT
 * Add your custom error reporting middleware here
 * Example:
 *   app.use(function(err, req, resp, next) {
 *     console.log(req.url, ' failed: ', err.stack);
 *     next(err);
 *   });
 */

// The ultimate error handler.
app.use(loopback.errorHandler());


/*
 * 5. Add a basic application status route at the root `/`.
 *
 * (remove this to handle `/` on your own)
 */

app.get('/', loopback.status());

/*
 * 6. Enable access control and token based authentication.
 */

var swaggerRemote = app.remotes().exports.swagger;
if (swaggerRemote) swaggerRemote.requireToken = false;

// model extensions
require('./models/project');
require('./models/model-definition');
require('./models/datasource-definition');

// server middleware
app.use(loopback.favicon());
app.use(loopback.logger('dev'));
app.use(loopback.bodyParser());
app.use(loopback.methodOverride());
app.use(app.router);

// development only
if ('development' == app.get('env')) {
  app.use(loopback.errorHandler());
}

// only start the server if this module
// is the main module...
if(require.main === module) {
  app.listen();
}