Modules

Modules are reusable pieces of code in a file that can be exported and then imported for use in another file, which allows the creation of programs whose components can be separated, used individually, and recombined to create a complete system.

• We can export modules using the export keyword and import them in other files using the import keyword

math.js

export function add(a, b) { // Exporting functions
    return a + b;
}

app.js

import { add } from './math.js'; // We define the path of the external file
const add = require('./math.js'); // Or using Node.js syntax

console.log(add(2, 3)); // Exports are saved with the same name

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• We can also do multiple exports and imports at the same time, and export variables too

math.js

function add(a, b) {
    return a + b;
}
function mult(a, b) { 
    return a * b;
}

let pi = 3.14; // Exporting a variable

export { add, mult, pi }; // Exporting multiple items

app.js

import { add, mult, pi } from './math.js'; // Importing multiple functions

console.log(add(2, 3));
console.log(mult(2, 3));
console.log(pi);

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• We can also set a custom name for the imports by using the as keyword

math.js

function adding(a, b) {
    return a + b;
}
function multiply(a, b) { 
    return a * b;
}

export { adding, multiply }; // Export the variables with their name

app.js

import { adding as add, multiply as mult } from './math.js'; // Using custom names 

console.log(add(2, 3)); // Calling by the changed names
console.log(mult(2, 3));

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• We can also define a default export, which is a way to specify a single item as the main thing a module provides. This value can be imported without using curly braces in the importing file, and any name can be chosen when importing it

math.js

function add(a, b) {
    return a + b;
}
function mult(a, b) { 
    return a * b;
}

export default add; // Exporting multiple items

app.js

import addition from './math.js'; // Importing the default item

console.log(addition(4, 3));