Question

How to include a JavaScript file in another JavaScript file?

I'm working on a project where I need to modularize my code by splitting it into multiple JavaScript files for better organization. I want to know how I can include a JavaScript file inside another JavaScript file so that I can use the functions and variables defined in one file within another. What’s the best way to achieve this?

Answer 1

Let's assume you have two files:

1. math.js: This file contains a simple function to add two numbers.

2. app.js: This file will import the math.js functions and use them.

1. Exporting from the first file (math.js)

In the file where you define your functions or variables (math.js in this case), you need to export them using module.exports.

math.js:

// math.js

// Define a function

function add(a, b) {

    return a + b;

}

// Export the function so it can be used in other files

module.exports = {

    add

};

Here, we are exporting the add function from math.js so that other files can import and use it.

2. Importing in the second file (app.js)

In the file where you want to use the functions from another file (app.js in this case), you import the functions using the require() function.

app.js:

// app.js

// Import the `add` function from the `math.js` file

const math = require('./math');

// Use the imported function

const result = math.add(3, 5);

console.log(`The sum is: ${result}`);

In this file:

• require('./math') imports the module (i.e., math.js), and the result is assigned to the math variable.

• We then access the add function from the math module using math.add().