This article shows how you can include another JS (Javascript) file into your main application JS file.
We can have a situation where we store configuration settings or database settings in another file. It can be .js, .env, .json or any other file. We will be using module.exports object to achieve this.
I have created a folder named “nodejs” inside my Documents folder. And, then created a simple Node.js app over there.
mukesh:nodejs chapagain$ pwd
/Users/mukeshchapagain/Documents/nodejs
mukesh:nodejs chapagain$ ls
app.js config
Including JS file
Here,
– the main application file is
app.js
– the file to be included is in config folder:config/settings.js
We include the config/settings.js file in our main app js file i.e. app.js.
1) RETURN SIMPLE STRING
include/settings.js
module.exports = 'Hello World';
app.js
var settings = require('./config/settings');
console.log(settings);
Output
mukesh:nodejs chapagain$ node app.js
Hello World
2) RETURN PROPERTY / METHOD
include/settings.js
module.exports.myMessage = 'My simple message';
app.js
var settings = require('./config/settings');
console.log(settings);
console.log(settings.myMessage);
Output
mukesh:nodejs chapagain$ node app.js
{ myMessage: 'My simple message' }
My simple message
3) RETURN METHOD / FUNCTION
include/settings.js
module.exports.myMessage = 'My simple message';
module.exports.add = function(num1, num2) {
return num1 + num2;
}
app.js
var settings = require('./config/settings');
console.log(settings);
console.log(settings.myMessage);
console.log(settings.add(1, 2));
Output
mukesh:nodejs chapagain$ node app.js
{ myMessage: 'My simple message', add: [Function] }
My simple message
3
4) RETURN JSON OBJECT
We can export a JSON object that can contain variable and functions within it.
include/settings.js
var addFunc = function(num1, num2) {
return num1 + num2;
}
module.exports = {
myMessage: 'My simple message',
add: addFunc
}
app.js
var settings = require('./config/settings');
console.log(settings);
console.log(settings.myMessage);
console.log(settings.add(1, 2));
Output
mukesh:nodejs chapagain$ node app.js
{ myMessage: 'My simple message', add: [Function] }
My simple message
3
Including JSON file
You don’t require export statements for getting data from JSON files.
Here,
– the main application file is
app.js
– the JSON file to be included is in config folder:config/settings.json
We include the config/settings.json file in our main app js file i.e. app.js.
include/settings.json
{
"myMessage": "My simple message",
"anotherMessage": "Another Message"
}
app.js
var settings = require('./config/settings.json');
console.log(settings);
console.log(settings.myMessage);
console.log(settings.anotherMessage);
Output
mukesh:nodejs chapagain$ node app.js
{ myMessage: 'My simple message',
anotherMessage: 'Another Message' }
My simple message
Another Message
Including ENV file
We will install the dotenv module to access the .env file contents.
npm install dotenv --save
Here,
– the main application file is
app.js
– the environment variables are stored in.env
Note:
Remember to ignore the .env file in your git repository by creating a .gitignore file and adding the .env line over there. Otherwise, your private information stored in the .env file might get exposed.
dotenv module is used to include the .env file in our main app js file.
.env
DB_HOST=localhost
DB_USER=yourDbUsername
DB_PASS=yourDbPassword
app.js
require('dotenv').config(); // include .env file
let db = {
host: process.env.DB_HOST,
username: process.env.DB_USER,
password: process.env.DB_PASS
};
console.log(db);
Output
mukesh:nodejs chapagain$ node app.js
{ host: 'localhost',
username: 'yourDbUsername',
password: 'yourDbPassword' }
Hope this helps. Thanks.