How to modularize code in node js

Question

I am new to Node. I have done a sample application where I have done all the code in one file server.js

var express = require('express'),
                nconf=require('nconf');
            var app = express()
            nconf.env().file({ file: 'db-config.json'});
            app.use(express.static(__dirname+"\\client"));
            var dbConfig = nconf.get();
            console.log();
            var mysql      = require('mysql');
            var connection = mysql.createConnection({
                        host: dbConfig.hostname,
                        port: dbConfig.port,
                        user: dbConfig.user,
                        password: dbConfig.password,
                        database: dbConfig.db
            });

            app.get('/', function (req, res) {
                 res.sendFile(__dirname+"\\client\\index.html");
            })
            app.get('/getTables', function (req, res) {
                     var sql="SELECT table_name as text from information_schema.tables where table_schema = ?";
                     connection.query(sql,[dbConfig.db],function(err,rows,fields){
                     if(!err){
                      var data={

                           "children":[]
                      };
                      for(var i=0;i<rows.length;i++){
                        rows[i].leaf=true;
                        data.children.push(rows[i]);
                      }
                       res.json(data);
                     }else{
                     console.log("db not connected");
                     }

                     });

            })
            var server = app.listen(3000, function () {

              var host = server.address().address
              var port = server.address().port

              console.log('Example app listening at http://%s:%s', host, port)

            })

I want to know how to write all my mysql config code in one file and use where ever i want. And I want to write client response creation in another fie.

since you're using express js I recommend you to type in console: npm install express-generator -g this will create for you template project with initial structure. All folder like routes, views, javascripts and etc. From there you also will see how everytying is connected, but any way you should use require like in the answer below. — Nicolai
– Nicolai, Commented Feb 16, 2015 at 19:48

Nicolai · Accepted Answer · 2015-02-16 20:16:04Z

As I remember there are two ways how you can exports methods or objects from other modules:

module.exports
using:

//yourModule.js

function method1(){    
}

to export this function we can do the following:

module.exports = method1;

in this case when you will use var myModule = require("./yourModule") - the myModule will be method1, i.e. to call it you will simply call myModule().

or you can exports like:

module.exports = { 
    method1: method1,
    method2: ...
}

in this case when you will use require like in case above to call functions you will need to type: myModule.method1();

the 2nd way is to use directly:

exports.method1 = function (){}; exports.method2 = function (){}; exports.someObject = {};

and this will be the same as:

module.exports = { 
        method1: method1,
        method2: ...
    }

Reference

P.S. since you're using express js I recommend you to type in console: npm install express-generator -g this will create for you template project with initial structure. All folder like routes, views, javascripts and etc.

Steve H. · Accepted Answer · 2015-02-16 19:57:00Z

1

Use require:

var someModule= require('./myModule');

Edit:

Read about node.js modules here: http://nodejs.org/api/modules.html#modules_modules

edited Feb 16, 2015 at 19:57

answered Feb 16, 2015 at 19:35

Steve H.

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1 Comment

Nick Tomlin Over a year ago

while this is absolutely correct, some background information about about splitting the code into individual modules and then requiring them would be helpful :)

utnas · Accepted Answer · 2015-02-16 19:48:20Z

0

You can write an api for you DB module and require this module in your main file.

var mysql = require('mysql');

...

connect = function (dbConfig) {
    mysql.createConnection({
        host: dbConfig.hostname,
        port: dbConfig.port,
        user: dbConfig.user,
        password: dbConfig.password,
        database: dbConfig.db
    });
};

select = function (req, res) {
    var sql = "SELECT table_name as text from information_schema.tables where table_schema = ?";
    connection.query(sql, [dbConfig.db], function (err, rows, fields) {
        if (!err) {
            var data = {
                "children": []
            };
            for (var i = 0; i < rows.length; i++) {
                rows[i].leaf = true;
                data.children.push(rows[i]);
            }
            res.json(data);
        } else {
            console.log("db not connected");
        }
    });
};

In your main file you can require this file.

var myDBAPI = require('./myDBAPI');

app.get('/', function (req, res) {
  res.sendFile(__dirname+"\\client\\index.html");
});

app.get('/getTables', myDBAPI.select(req, res));

PS: Don't forget ; after instructions

answered Feb 16, 2015 at 19:48

utnas

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1 Comment

utnas Over a year ago

You should separate file with a singke responsability. Your DBAPI should be in a separeted file. In this case you case you can test it separetly.

Zeck · Accepted Answer · 2017-08-31 12:06:47Z

0

You can use Environment Variables, to setup your server and database params.

Use node-env-file module, to load this settings from .env file:

dev.env

DATABASE_URL=localhost:3306 DATABASE_USERNAME=root DATABASE_PASSWORD= SERVER_IP=127.0.0.1 SERVER_PORT=3000

Usage:

app.listen(process.env.SERVER_IP || '127.0.0.1', process.env.SERVER_PORT || 3000);

https://www.npmjs.com/package/node-env-file

answered Aug 31, 2017 at 12:06

Zeck

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