JavaScript Program to Include a JS file in Another JS file

Example: Using import/export

Let's create a file named module.js (filename can be anything) with the following content:

// program to include JS file into another JS file

const message = 'hello world';

const number = 10;

function multiplyNumbers(a, b) {
    return a * b;
}

// exporting variables and function
export { message, number, multiplyNumbers };

In order to include these variables and functions in another file, say main.js, you can use the import keyword as:

// import the variables and function from module.js
import { message, number, multiplyNumbers } from './modules.js';

console.log(message); // hello world

console.log(number); // 10

console.log(multiplyNumbers(3, 4)); // 12
console.log(multiplyNumbers(5, 8)); // 40

To include another file, you have to export the code that you want to use in another file using the export statement. For example,

export { message, number, multiplyNumbers };

You could also do individual export. For example,

export const message = 'hello world';

export const number = 10;

To include code from another file, you have to use the import statement and import using the file path. For example,

// importing codes from module file
import { message, number, multiplyNumbers } from './modules.js';

Then, you can use these codes as they are a part of the same file.

This helps in writing cleaner, maintainable, and modular code.