freeCodeCamp/
├── api/                   # Fastify API server (TypeScript)
├── client/                # Gatsby/React frontend (TypeScript)
├── curriculum/            # All challenges and certifications (YAML/Markdown)
│   └── challenges/
│       ├── english/
│       │   ├── responsive-web-design/
│       │   ├── javascript-algorithms-and-data-structures/
│       │   └── ...
│       └── ...
├── tools/
│   ├── challenge-helper-scripts/  # CLI tools for curriculum authoring
│   └── ui-components/             # Shared React components
├── config/                # Shared configuration
└── e2e/                   # Playwright end-to-end tests

git clone https://github.com/<YOUR_USERNAME>/freeCodeCamp.git
cd freeCodeCamp

pnpm install

cp sample.env .env

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pnpm run seed

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// This is an in-line comment.
/* This is a multi-line comment */

assert(code.match(/(\/\/)/).length > 0);

assert(code.match(/(\/\*[\s\S]+?\*\/)/).length > 0);

// Your starting code here

// inline comment
/* multi-line
   comment */

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3. Follow the challenge file format above

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assert.match(code, /let\s+myVariable/);

assert.strictEqual(myFunction(42), true);

const el = document.getElementById('main');
assert.exists(el);

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// DOM access (for HTML challenges)
document.querySelector('#my-id')
document.getElementById('test')

// Code inspection
assert.match(code, /regex/);          // raw source code string
assert.include(code, 'someString');

// Value assertions (Chai-style)
assert.strictEqual(actual, expected);
assert.isTrue(value);
assert.exists(value);
assert.approximately(actual, expected, delta);

// For async challenges
// Use __helpers object
const result = await fetch('/api/test');
assert.strictEqual(result.status, 200);

// api/src/routes/example.ts
import { type FastifyPluginCallbackTypebox } from '../helpers/plugin-callback-typebox';
import { Type } from '@fastify/type-provider-typebox';

export const exampleRoutes: FastifyPluginCallbackTypebox = (
  fastify,
  _options,
  done
) => {
  fastify.get(
    '/example/:id',
    {
      schema: {
        params: Type.Object({
          id: Type.String()
        }),
        response: {
          200: Type.Object({
            data: Type.String()
          })
        }
      }
    },
    async (req, reply) => {
      const { id } = req.params;
      return reply.send({ data: `Result for ${id}` });
    }
  );

  done();
};

// api/src/app.ts - register the plugin
import { exampleRoutes } from './routes/example';

await fastify.register(exampleRoutes, { prefix: '/api' });

// api/src/schemas/user.ts
import mongoose from 'mongoose';

const userSchema = new mongoose.Schema({
  email: { type: String, required: true, unique: true },
  completedChallenges: [
    {
      id: String,
      completedDate: Number,
      solution: String
    }
  ]
});

export const User = mongoose.model('User', userSchema);

// client/src/pages/my-new-page.tsx
import React from 'react';
import { Helmet } from 'react-helmet';
import { useTranslation } from 'react-i18next';

const MyNewPage = (): JSX.Element => {
  const { t } = useTranslation();

  return (
    <>
      <Helmet>
        <title>{t('page-title.my-new-page')} | freeCodeCamp.org</title>
      </Helmet>
      <main>
        <h1>{t('headings.my-new-page')}</h1>
      </main>
    </>
  );
};

export default MyNewPage;

// client/src/redux/selectors.ts pattern
import { createSelector } from 'reselect';
import { RootState } from './types';

export const userSelector = (state: RootState) => state.app.user;

export const completedChallengesSelector = createSelector(
  userSelector,
  user => user?.completedChallenges ?? []
);

// In a component
import { useAppSelector } from '../redux/hooks';
import { completedChallengesSelector } from '../redux/selectors';

const MyComponent = () => {
  const completedChallenges = useAppSelector(completedChallengesSelector);
  return <div>{completedChallenges.length} challenges completed</div>;
};

// Add keys to client/i18n/locales/english/translations.json
{
  "my-component": {
    "title": "My Title",
    "description": "My description with {{variable}}"
  }
}

// Use in component
const { t } = useTranslation();
t('my-component.title');
t('my-component.description', { variable: 'value' });

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// e2e/my-feature.spec.ts
import { test, expect } from '@playwright/test';

test('user can complete a challenge', async ({ page }) => {
  await page.goto('/learn/javascript-algorithms-and-data-structures/basic-javascript/comment-your-javascript-code');

  // Fill in the code editor
  await page.locator('.monaco-editor').click();
  await page.keyboard.type('// inline comment\n/* block comment */');

  // Run tests
  await page.getByRole('button', { name: /run the tests/i }).click();

  // Check results
  await expect(page.getByText('Tests Passed')).toBeVisible();
});

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responsive-web-design/
javascript-algorithms-and-data-structures/
front-end-development-libraries/
data-visualization/
relational-database/
back-end-development-and-apis/
quality-assurance/
scientific-computing-with-python/
data-analysis-with-python/
machine-learning-with-python/
coding-interview-prep/
the-odin-project/
project-euler/

responsive-web-design/
├── basic-html-and-html5/
├── basic-css/
├── applied-visual-design/
├── css-flexbox/
└── css-grid/

// tools/challenge-helper-scripts/helpers/id-gen.ts
import { ObjectId } from 'bson';
export const generateId = (): string => new ObjectId().toHexString();

forumTopicId: 301090  # Must be a real forum post ID

{
  "name": "Basic JavaScript",
  "dashedName": "basic-javascript",
  "order": 0,
  "time": "5 hours",
  "template": "",
  "required": [],
  "isUpcomingChange": false,
  "isBeta": false,
  "isLocked": false,
  "isPrivate": false
}

// In e2e tests, use the test user fixture
import { authedUser } from './fixtures/authed-user';

test.use({ storageState: 'playwright/.auth/user.json' });

test('authenticated action', async ({ page }) => {
  // page is already logged in
  await page.goto('/settings');
  await expect(page.getByText('Account Settings')).toBeVisible();
});

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Commit message prefixes: `fix:`, `feat:`, `chore:`, `docs:`, `refactor:`, `test:`

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