CommonJS require and module.exports in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does require() do in CommonJS?

require() loads and runs a module file, returning the exported values from that module.

beginner

How do you export a single function or object in CommonJS?

You assign it to module.exports. For example: module.exports = myFunction;

intermediate

What is the difference between exports and module.exports?

exports is a shortcut to module.exports. Reassigning exports breaks the link, so only module.exports controls what is exported.

beginner

Can you require a JSON file using require() in CommonJS?

Yes, require() can load JSON files and returns the parsed object.

intermediate

What happens if you call require() multiple times for the same module?

The module is loaded once and cached. Subsequent require() calls return the cached exports, not re-running the module code.

Which statement correctly exports a function named sayHello in CommonJS?

A exports = sayHello;

B module.exports = sayHello;

C export default sayHello;

D require('sayHello');

Only module.exports = sayHello; correctly exports the function. Reassigning exports breaks the export link.

What does require('./math') return if math.js uses module.exports = { add, subtract }?

A Undefined

B A string with the file path

C An object with <code>add</code> and <code>subtract</code> functions

D A function named <code>math</code>

The require() call returns the object assigned to module.exports, which contains the add and subtract functions.

If you want to export multiple values, which is the best way in CommonJS?

A Use <code>require()</code> inside the module

B Call <code>exports = value1, value2</code>

C Use <code>export { value1, value2 }</code>

D Assign an object to <code>module.exports</code> with all values

Assigning an object with multiple properties to module.exports is the standard way to export multiple values.

What happens if you do exports = { a: 1 } instead of module.exports = { a: 1 }?

A The module exports remain unchanged (empty object)

B The module exports the object { a: 1 }

C An error is thrown

D The module exports a function

Reassigning exports breaks the link to module.exports, so the exported object stays as the default empty object.

How does CommonJS handle circular dependencies between modules?

A It returns a partially loaded module object during the cycle

B It throws an error immediately

C It ignores the second require call

D It reloads the module twice

CommonJS returns a partially loaded module object during circular dependencies to avoid infinite loops.

Explain how require() and module.exports work together in CommonJS modules.

Think about how you share code between files.

Describe the difference between exports and module.exports and why it matters.

Consider what happens if you assign a new object to exports.