Node.js Fundamentals · Modules & npm · Lesson 4 of 13
CommonJS Modules
Concept
CommonJS Modules
require() imports code from other files or packages. module.exports shares code from the current file.
By the end of this lesson
- Explain the core idea behind CommonJS Modules.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
ExampleRunnable
// math.js
module.exports.add = (a, b) => a + b;
// app.js
const { add } = require("./math");Self-check before continuing
Without looking at the example, describe what changes when you modify one input in CommonJS Modules. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Explain what module.exports lets other files access.
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