Node.js 如何建立可以从其他文件访问的全局mongodb连接

我有一个主服务器文件index.js：

const express = require('express')
const app = express()

const route = require('./route')

app.use('/main', route)
app.listen(3000)

然后我有route.js文件：

const express = require('express')
const router = express.Router()

router.get('/', (req, res) => {
  res.send('Hello from main')
})

module.exports = router

正如标题所示，我如何建立全局mongodb连接，从而不必在每条路由上建立到数据库的新连接？

---

谢谢

我很惊讶没有答案。最常见的模式是在单独的模块中初始化数据库连接，并将其导入任何需要它的文件中

以下内容摘自这篇较长的文章，采用回调风格编写。我对其进行了一些更新，以保证其符合以下要求：

/* Callback Style */

const assert = require("assert");
const client = require("mongodb").MongoClient;
const config = require("../config");
let _db;
module.exports = {
    getDb,
    initDb
};

function initDb(callback) {
  if (_db) {
    console.warn("Trying to init DB again!");
    return callback(null, _db);
  }
  client.connect(config.db.connectionString, 
  config.db.connectionOptions, connected);
  function connected(err, db) {
    if (err) {
      return callback(err);
    }
    console.log("DB initialized - connected to: " + 
      config.db.connectionString.split("@")[1]);
    _db = db;
    return callback(null, _db);
  }
}

function getDb() {
  assert.ok(_db, "Db has not been initialized. Please called init first.");
  return _db;
}

 /******************************************************************/
//The client
const initDb = require("./db").initDb;
const getDb = require("./db").getDb;
const app = require("express")();
const port = 3001;
app.use("/", exampleRoute);
initDb(function (err) {
    app.listen(port, function (err) {
        if (err) {
            throw err; //
        }
        console.log("API Up and running on port " + port);
    });
);
function exampleRoute(req, res){
 const db = getDb();
 //Do things with your database connection
 res.json(results);
}

这是一个基于承诺的版本，没有分号，这是我自己可能做的。这些功能都将成为项目间重用的候选功能

const assert = require("assert")
const client = require("mongodb").MongoClient
const config = require("../config")
let _db
module.exports = {
    getDb,
    initDb
}

function initDb() {
  if (_db) {
    console.warn("Trying to init DB again!");
    return Promise.resolve(true)
  }
  return client.connect(config.db.connectionString, 
  config.db.connectionOptions)
}

function getDb() {
  assert.ok(_db, "Db has not been initialized. Please called init first.")
  return _db
}

//////////////////////


const {initDb, getDb} = require("./db")
const app = require("express")()
const port = 3001

app.use("/", exampleRoute)

initDb().
    then(_ =>bootServer(port))
    .catch(console.log)

function bootServer(port) {
    app.listen(port, function (err) {
        if (err) {
            Promise.reject(err)
        }
        console.log("API Up and running on port " + port)
        Promise.resolve()
    })   
}    

function exampleRoute(req, res){
 const db = getDb();
 //Do things with your database connection
 res.json(results);
}

---

我很惊讶没有人回答这个问题。最常见的模式是在单独的模块中初始化数据库连接，并将其导入任何需要它的文件中

以下内容摘自这篇较长的文章，采用回调风格编写。我对其进行了一些更新，以保证其符合以下要求：

/* Callback Style */

const assert = require("assert");
const client = require("mongodb").MongoClient;
const config = require("../config");
let _db;
module.exports = {
    getDb,
    initDb
};

function initDb(callback) {
  if (_db) {
    console.warn("Trying to init DB again!");
    return callback(null, _db);
  }
  client.connect(config.db.connectionString, 
  config.db.connectionOptions, connected);
  function connected(err, db) {
    if (err) {
      return callback(err);
    }
    console.log("DB initialized - connected to: " + 
      config.db.connectionString.split("@")[1]);
    _db = db;
    return callback(null, _db);
  }
}

function getDb() {
  assert.ok(_db, "Db has not been initialized. Please called init first.");
  return _db;
}

 /******************************************************************/
//The client
const initDb = require("./db").initDb;
const getDb = require("./db").getDb;
const app = require("express")();
const port = 3001;
app.use("/", exampleRoute);
initDb(function (err) {
    app.listen(port, function (err) {
        if (err) {
            throw err; //
        }
        console.log("API Up and running on port " + port);
    });
);
function exampleRoute(req, res){
 const db = getDb();
 //Do things with your database connection
 res.json(results);
}

这是一个基于承诺的版本，没有分号，这是我自己可能做的。这些功能都将成为项目间重用的候选功能

const assert = require("assert")
const client = require("mongodb").MongoClient
const config = require("../config")
let _db
module.exports = {
    getDb,
    initDb
}

function initDb() {
  if (_db) {
    console.warn("Trying to init DB again!");
    return Promise.resolve(true)
  }
  return client.connect(config.db.connectionString, 
  config.db.connectionOptions)
}

function getDb() {
  assert.ok(_db, "Db has not been initialized. Please called init first.")
  return _db
}

//////////////////////


const {initDb, getDb} = require("./db")
const app = require("express")()
const port = 3001

app.use("/", exampleRoute)

initDb().
    then(_ =>bootServer(port))
    .catch(console.log)

function bootServer(port) {
    app.listen(port, function (err) {
        if (err) {
            Promise.reject(err)
        }
        console.log("API Up and running on port " + port)
        Promise.resolve()
    })   
}    

function exampleRoute(req, res){
 const db = getDb();
 //Do things with your database connection
 res.json(results);
}

---

感谢您的快速回复！感谢您的快速回复！