ES Modules
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Expert Answer & Key Takeaways
Mastering ES Modules is essential for high-fidelity technical architecture and senior engineering roles in 2026.
JavaScript Modules
JavaScript modules allow you to break up your code into separate files. This makes it easier to maintain the code-base and share functionality across different parts of an application.
1. Export and Import
Modules are based on the
export and import statements.
Named Exports:// person.js
export const name = "Jesse";
export const age = 40;Importing Named Exports:
import { name, age } from "./person.js";2. Default Exports
You can only have one default export in a file.
// message.js
const message = () => {
return "Hello World";
};
export default message;Importing Default Export:
import message from "./message.js";When importing a default export, you can give it any name you like during the import statement.
3. Benefits of Modules
- Maintainability: Smaller files are easier to manage and fix.
- Namespacing: Variables inside a module are not global; they won't conflict with other scripts.
- Reusability: Exported code can be used in multiple parts of the application or even in different projects.
4. Modules in HTML
To use modules in a browser, you must set the
type attribute to "module" in the script tag.<script type="module" src="main.js"></script>[!IMPORTANT] Modules always run in strict mode by default, and they are always loaded asynchronously.
Top Interview Questions
?Interview Question
Q:Difference between Named and Default exports?
A:
A file can have multiple named exports but only one default export. Named exports must be imported using curly braces with matching names, while default exports can be imported without braces and assigned any local name.
?Interview Question
Q:Are modules always in strict mode?
A:
Yes. JavaScript modules automatically use 'strict mode' by default, even if you don't use the 'use strict' directive.
?Interview Question
Q:Can you import modules within an HTML <script> without type='module'?
A:
No. Standard scripts do not support the 'import' or 'export' statements. You must specify type='module' for the browser to handle modular JavaScript.
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