如何使用async/await从导出模块获取结果 [英] How can i get result from export module using async/await

问题描述

如何使用async/await或promise ...将client.db(db_name)从导出模块获取到main.js中...

How can i get client.db(db_name) from export module to main.js using async/await or promise ...

main.js

var express = require('express')
var app = express();

enter code here
// Web server port number.
const port = 4343;

require('./config/app_config')(app);
db = require('./config/data_config')(app);
db.collection('users');


app.listen(port, () => {
    console.log(`Server start at port number: ${port}`);
});

config.js

  module.exports = (app) => {
  const mongo_client = require('mongodb').MongoClient;
  const assert = require('assert');

  const url = 'mongodb://localhost:27017';
  const db_name = 'portfolio';

  mongo_client.connect(url, (err, client) => {
    assert.equal(null, err);
    console.log('Connection Successfully to Mongo');
    return client.db(db_name);
  });
};

推荐答案

从您的config.js文件中返回承诺. mongodb客户端直接支持诺言，只是不通过回调参数，并使用then.

Return a promise from your config.js file. mongodb client supports promises directly, just do not pass the callback parameter and use then.

config.js

module.exports = (app) => {
  const mongo_client = require('mongodb').MongoClient;
  const assert = require('assert');

  const url = 'mongodb://localhost:27017';
  const db_name = 'portfolio';

  return mongo_client.connect(url).then(client => {
    assert.equal(null, err);
    console.log('Connection Successfully to Mongo');
    return client.db(db_name);
  });
};

然后调用，然后在promise处理程序中进行其余操作:

And call then and do the rest in the promise handler:

main.js

var express = require('express')
var app = express();

// Web server port number.
const port = 4343;

require('./config/app_config')(app).then(db => {
  db.collection('users');
});

// as Bergi suggested in comments, you could also move this part to `then` 
// handler to it will not start before db connection is estabilished
app.listen(port, () => {
  console.log(`Server start at port number: ${port}`);
});

这篇关于如何使用async/await从导出模块获取结果的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！