JavaScript modules

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JavaScript Modules

JavaScript modules are a way to organize code into reusable components. Modules help you manage the complexity in large-scale JavaScript applications. Modules promote code reuse and maintainability. In ES6, the standard version of JavaScript, modules are natively supported. You can use the import and export keywords to define dependencies between modules and share functionality between different parts of your code.

JavaScript modules have benefits over older module systems like CommonJS. They provide a standardized syntax and are optimized for browser environments. Modules can be asynchronously loaded, improving performance by reducing initial load times. Modules support tree-shaking, a technique that eliminates unused code during the build process.

To use modules in JavaScript, you should create separate files for each module and use the export keyword to expose specific values, functions, or classes. Then, in other files, you should use the import keyword to bring those exported entities into scope.

Module best practices include keeping modules small, limiting dependencies, and descriptive naming.

JavaScript Modules Example

Here's an example that demonstrates JavaScript modules:

// math.js - Module file
export function add(a, b) {
  return a + b;
}

export function subtract(a, b) {
  return a - b;
}

// app.js - Main file
import { add, subtract } from './math.js';

// Usage
const result1 = add(5, 3);
const result2 = subtract(10, 4);

console.log(result1); // Output: 8
console.log(result2); // Output: 6

In this example, we have two files: math.js, which defines two functions, add and subtract, and app.js, which imports these functions and uses them to perform calculations. The export keyword allows us to make the functions available for import in other files, and the import statement brings them into the scope of the app.js file.

JavaScript Modules FAQ (Interview Questions and Answers)

1. What are modules in JavaScript?
   A way to organize and structure code into reusable components
   Variables used to store data in JavaScript
   Built-in functions in JavaScript
   
2. What are CommonJS modules?
   Modules that are uncommonly used in JavaScript
   An older module system used in Node.js and non-browser environments
   Modules that are common to all JavaScript projects
   
3. What is the difference between JavaScript modules and classes?
   JavaScript modules are used for styling, while classes are used for functionality.
   JavaScript modules and classes are the same thing.
   JavaScript modules organize and share code, while classes define object blueprints.
   
4. Can JavaScript modules be used in the browser?
   Yes, JavaScript modules are supported in modern browsers
   No, JavaScript modules can only be used in Node.js.
   JavaScript modules can only be used in specific browsers.
   
5. What is the best practice for using JavaScript modules?
   Keeping modules small, limiting dependencies, and descriptive naming
   Combining all code into a single module for simplicity
   Using as many dependencies as possible to enhance functionality
   

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