问在node.js web应用程序中全局定义PostgreSQL数据库连接变量是最佳实践吗？

EN

var promise = require('bluebird');

/**
 *Use dotenv to read .env vars into Node
 */
require('dotenv').config();

const  options = {
  // Initialization Options
  promiseLib: promise,
  connect(client, dc, useCount) {
    const cp = client.connectionParameters;
    console.log('Connected to database:', cp.database);
  }
};

const  pgp = require('pg-promise')(options);
const  connectionString = process.env.PG_CONN_STR;
const  db = pgp(connectionString);

module.exports = {
    pgp, db
};

var db_global = require('./db');
var db = db_global.db;

// add query functions

module.exports = {
  getAllLocations: getAllLocations,
  getLocation: getLocation,
  createLocation: createLocation,
  updateLocation: updateLocation,
  removeLocation: removeLocation
};

function getAllLocations(req, res, next) {
  db.any('select * from gcur_point_location')
    .then(function (data) {
      res.status(200)
        .json({
          status: 'success',
          data: data,
          message: 'Retrieved ALL GCUR Point Locations'
        });
    })
    .catch(function (err) {
      return next(err);
    });
}

function getLocation(req, res, next) {
  var locationId = parseInt(req.params.id);
  db.one('select * from gcur_point_location where locationid = $1', locationId)
    .then(function (data) {
      res.status(200)
        .json({
          status: 'success',
          data: data,
          message: 'Retrieved ONE Location by Id'
        });
    })
    .catch(function (err) {
      return next(err);
    });
}

function createLocation(req, res, next) {
  req.body.age = parseInt(req.body.age);
  db.none('insert into gcur_point_location(locationname, locationstatus, lng, lat)' +
      'values(${locationname}, ${locationstatus}, ${lng}, ${lat})',
    req.body)
    .then(function () {
      res.status(200)
        .json({
          status: 'success',
          message: 'Inserted one Location'
        });
    })
    .catch(function (err) {
      return next(err);
    });
}

function updateLocation(req, res, next) {
  db.none('update gcur_point_location set locationname=$1, locationstatus=$2, lng=$3, lat=$4 where locationid=$5',
    [req.body.locationname, req.body.locationstatus, parseFloat(req.body.lng),
      parseFloat(req.body.lat), parseInt(req.params.id)])
    .then(function () {
      res.status(200)
        .json({
          status: 'success',
          message: 'Updated Location'
        });
    })
    .catch(function (err) {
      return next(err);
    });
}

function removeLocation(req, res, next) {
  var locationId = parseInt(req.params.id);
  db.result('delete from gcur_point_location where locationid=$1', locationId)
    .then(function (result) {
      /* jshint ignore:start */
      res.status(200)
        .json({
          status: 'success',
          message: `Removed ${result.rowCount} Location`
        });
      /* jshint ignore:end */
    })
    .catch(function (err) {
      return next(err);
    });
}

var express = require('express');
var router = express.Router();

var db = require('../db/location');

/* GET home page. */
router.get('/', function(req, res, next) {
  res.render('index', { title: 'Express' });
});

router.get('/api/locations', db.getAllLocations);
router.get('/api/location/:id', db.getLocation);
router.post('/api/location', db.createLocation);
router.put('/api/location/:id', db.updateLocation);
router.delete('/api/location/:id', db.removeLocation);

module.exports = router;

var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');

var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', indexRouter);
app.use('/users', usersRouter);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

module.exports = app;