var pg = require('pg.js');
var pgTransact = require('pg-transact');
function transaction(client, cb){
  // everything in here is run as a transaction
  client.query('SELECT NOW() as when', function(err, result){
    if(err){
      // passing an error to the callback does a rollback on the transaction
      return cb(err);
    }
    // passing a `null` error and a result will resolve the transaction as the result
    cb(null, result);
  });
}
pg.connect(connectionString, function(err, client, done){
  if(err){
    throw err;
  }
  pgTransact(client, transaction, done)
    .then(console.log, console.error);
});

var pg = require('pg.js');
var pgTransact = require('pg-transact');
function transaction(client){
  return new Promise(function(resolve, reject){
    client.query('SELECT NOW() as when', function(err, result){
      if(err){
        return reject(err);
      }
      resolve(result);
    });
  });
}
pg.connect(connectionString, function(err, client, done){
  if(err){
    throw err;
  }
  pgTransact(client, transaction, done)
    .then(console.log, console.error);
});