Node.js Fundamentals · Building an API · Lesson 11 of 13
Environment Variables
Concept
Environment Variables
process.env lets you read configuration, like ports or API keys, from outside your code, keeping secrets out of source files.
By the end of this lesson
- Explain the core idea behind Environment Variables.
- 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
const port = process.env.PORT || 3000;
console.log("Server running on port " + port);Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Environment Variables. 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
Write code that reads a DATABASE_URL environment variable with a fallback default.
Loading editor…
Console