JavaScript Exercises

A collection of JavaScript practice exercises with automated tests using Jest.

Prerequisites

Before you begin, make sure you have the following installed on your computer:

• Node.js (version 14 or higher)
  • Download from nodejs.org
  • To check if you have it installed, run: node --version
• npm (comes with Node.js)
  • To check if you have it installed, run: npm --version

Getting Started

1. Install Dependencies

First, you need to install the testing framework (Jest) and other dependencies. Open your terminal in this project directory and run:

npm install

This will download all the necessary packages into a node_modules folder.

2. Understanding the Structure

Each exercise is in its own folder under javascript-exercises/:

javascript-exercises/
├── 01_helloWorld/
│   ├── helloWorld.js          # Your code goes here
│   ├── helloWorld.spec.js     # Tests for this exercise
│   └── solution/              # Reference solution (don't peek!)
├── 02_addNumbers/
│   ├── addNumbers.js
│   ├── addNumbers.spec.js
│   └── solution/
└── ...

Running Tests

Run All Tests

To run all tests in the project:

npm test

This will run every test file and show you which exercises are passing and which are failing.

Run Tests for a Specific Exercise

To run tests for just one exercise, specify the path:

npm test 01_helloWorld

Or be more specific:

npm test javascript-exercises/01_helloWorld/helloWorld.spec.js

Watch Mode (Recommended for Development)

Watch mode automatically re-runs tests when you save your files:

npm run test:watch

To watch a specific exercise:

npm run test:watch -- 01_helloWorld

Press q to quit watch mode.

Verbose Output

For more detailed test output:

npm run test:verbose

Test Coverage

To see how much of your code is covered by tests:

npm run test:coverage

How to Work on an Exercise

1. Choose an exercise - Start with 01_helloWorld and work your way up
2. Read the test file - Open the .spec.js file to understand what's expected
3. Write your code - Edit the corresponding .js file
4. Run the tests - Use npm test <exercise-name> to check your work
5. Iterate - Keep refining your code until all tests pass

Example Workflow

# Start working on the helloWorld exercise
cd javascript-exercises/01_helloWorld

# Open the test file to see what's expected
cat helloWorld.spec.js

# Edit your solution
# (open helloWorld.js in your editor)

# Run the tests
npm test 01_helloWorld

# Keep editing and testing until all tests pass!

Understanding Test Output

When you run tests, you'll see output like this:

PASS  javascript-exercises/01_helloWorld/helloWorld.spec.js
  Hello World
    ✓ says "Hello, World!" (2 ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total

• ✓ means the test passed
• ✗ means the test failed (along with details about what went wrong)

If a test fails, Jest will show you:

• What was expected
• What your code actually returned
• The difference between them

Common Issues

"Cannot find module"

If you see this error, make sure you:

1. Ran npm install first
2. Are in the correct directory
3. Have the correct file paths in your require() statements

Tests aren't running

Make sure:

1. You're in the project root directory
2. You have node_modules folder (run npm install if not)
3. Your test file ends with .spec.js

"jest is not recognized"

This means Jest isn't installed. Run:

npm install

Tips for Beginners

1. Read the tests first - They tell you exactly what your function should do
2. Start simple - Get basic functionality working before handling edge cases
3. Use console.log() - Add console.log() statements to debug your code
4. Run tests frequently - Don't write too much code before testing
5. Check the solution if stuck - But try for at least 15-20 minutes first!

Additional Resources

• Jest Documentation
• MDN JavaScript Reference
• Node.js Documentation

Need Help?

If you're stuck:

1. Read the test file carefully - it shows exactly what's expected
2. Check the error messages - they often point to the problem
3. Try using console.log() to inspect your variables
4. Look at the solution files (but only after trying yourself!)

Happy coding!