NodeJS Identify once

Question

I want variable identify once so;

├── project_folder

| ├── app.js //main file

| └── router/index.js

app.js

const express = require('express');
const app = express();
const path = require('path');
const router = require('./router/index');
const mysql = require('mysql');

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

app.use('/',router);

app.listen( 8000, function(){
    console.log( 'Server listening on * 8000' );
});

index.js

//other codes
const connection = mysql.createConnection({
    host     : 'localhost',
    user     : 'root',
    password : 'root',
    database : 'wordpress'
});

connection.connect(function(err){
    if(err)
        console.log(err);   
});
//other codes

error : mysql is not defined

I don't want identify mysql and other variables again.

How can I solve?

Thank you for your helping.

SOLVED

Create a settings.js Define settings in file

EXAMPLE

const testSettings = "test Settings...";

module.exports = {
    test:testSettings
}

In a file you want require('./settings');

Using: settings.test

Node is modular, so you are not really supposed to create globals that way. Usually you create modules that exports something, and imports that module wherever you need it. — thsorens, Jul 05 '17 at 21:15
Just `require('mysql')` in any file you need. Trust me, it's much better that way, makes your code more modular, and is the way Node is intended to work. Making global variables is a big anti-pattern. — Mike Cluck, Jul 05 '17 at 21:17
@MustafaKÜÇÜK Inside of `index.js` put `const mysql = require('mysql')` just like you did in `app.js`. — Mike Cluck, Jul 05 '17 at 21:17
Is not it the crowd of code that makes every MySQL connection used anywhere? — Mustafa KÜÇÜK, Jul 05 '17 at 21:32

Miguel Mota · Answer 1 · 2017-07-05T21:23:34.370

0

You need to import the modules that are required:

index.js

const mysql = require('mysql');

const connection = mysql.createConnection({
    host     : 'localhost',
    user     : 'root',
    password : 'root',
    database : 'wordpress'
});

connection.connect(function(err) {
    if (err) {
        console.log(err); 
    }  
});

edited Jul 05 '17 at 21:23

answered Jul 05 '17 at 21:18

Miguel Mota

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Do I have to take it on every file? – Mustafa KÜÇÜK Jul 05 '17 at 21:19
@MustafaKÜÇÜK no, only in files where you are using `mysql` object – Miguel Mota Jul 05 '17 at 21:20

Sunny · Accepted Answer · 2017-07-05T22:15:37.413

You just need to require('mysql') in you index.js file.
And in your app.js file, as you have already imported this file(index.js), this will lead to the execution of this file as soon as it is required by you in app.js file.

Therefore, you need not require('mysql') in the app.js file as this is the way NODE intends to work (modularizes the code).

it must be required in each file where you us mysql

const mysql = require('mysql');

    const connection =

 mysql.createConnection({
        host     : 'localhost',
        user     : 'root',
        password : 'root',
        database : 'wordpress'
    });

    connection.connect(function(err) {
        if (err) {
            console.log(err); 
        }  
    });

If you create any functions inside this index.js file which are required in other modules, you can module.exports them.

Edit:

Refer to this link for in-depth explanation on modules: https://nodejs.org/api/modules.html

Is not it hard to define MySQL information in every file? – Mustafa KÜÇÜK Jul 05 '17 at 21:36 — Mustafa KÜÇÜK, Jul 05 '17 at 21:36
Not in every file but wherever you need to use mysql – Sunny Jul 05 '17 at 22:16 — Sunny, Jul 05 '17 at 22:16

score 0 · Answer 3 · answered Jul 05 '17 at 21:39

As others answers pointed, you should import module using 'require()' when you want to access it in the file.

If you are asking how to initialize db connection without initializing it in every file, you can create module for db connection.

Check Dave's answer on this topic how does createConnection work with nodeJS in mysql?

NodeJS Identify once

app.js

index.js

error : mysql is not defined

I don't want identify mysql and other variables again.

SOLVED

EXAMPLE

Using: settings.test

3 Answers3