JavaScript Data Types Lab

Master JavaScript data types and their built-in methods through 12 desi, story-based challenges! From Aadhaar masking to IRCTC PNR checking, each problem puts you in a real Indian scenario where you work with strings, numbers, arrays, objects, booleans, and type coercion.

Total: 100 points across 12 challenges

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Prerequisites

• Node.js v20 or higher
• Git
• A code editor (VS Code recommended)

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Getting Started

1. Accept the assignment

Click the GitHub Classroom invitation link shared by your instructor. This will create a personal copy of this repository under your GitHub account.

2. Clone your repository

git clone <your-repo-url>
cd js-datatypes-lab

Replace <your-repo-url> with the URL from your GitHub Classroom repo (the green Code button).

3. Install dependencies

npm install

4. Verify everything works

npm test

You should see all tests failing — that's expected! Your job is to make them pass.

Windows users: If npm test gives errors, use npm run test:win instead.

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How to Solve the Challenges

Step 1 — Open a challenge file

All challenges live in the src/ folder. Start with src/01-aadhaar-masker.js and work your way up.

src/
├── 01-aadhaar-masker.js          ← Start here
├── 02-chai-dukaan-menu.js
├── 03-bollywood-title-fixer.js
├── 04-gst-calculator.js
├── 05-mumbai-local-pass.js
├── 06-whatsapp-parser.js
├── 07-school-report-card.js
├── 08-ipl-auction-purse.js
├── 09-zomato-order-builder.js
├── 10-upi-transaction-log.js
├── 11-jugaad-form-validator.js
└── 12-railway-pnr-system.js

Step 2 — Read the story and rules

Each file has a detailed JSDoc comment at the top that explains:

• The kahani (story — a real Indian scenario)
• The rules your function must follow
• The parameters and return values
• Which built-in methods to use

Read it carefully — every edge case and requirement is described there.

Step 3 — Write your solution

Replace // Your code here with your implementation:

// Before
export function maskAadhaar(aadhaarNumber) {
  // Your code here
}

// After (example)
export function maskAadhaar(aadhaarNumber) {
  if (typeof aadhaarNumber !== 'string' || aadhaarNumber.length !== 12) {
    return "INVALID";
  }
  // ... your logic using slice, repeat, etc.
}

Step 4 — Run the test for that challenge

npm test -- 01-aadhaar

You can use any part of the filename to match:

npm test -- 02-chai
npm test -- 03-bollywood
npm test -- gst
npm test -- whatsapp
npm test -- zomato

Step 5 — Fix and repeat

If tests fail, read the error messages — they tell you exactly what was expected vs. what your function returned. Fix your code and run the test again.

Step 6 — Move to the next challenge

Once all tests pass for a challenge, move on to the next one. They get progressively harder.

Run all tests at once

npm test

Watch mode (auto re-run on save)

npm run test:watch

This re-runs tests every time you save a file — very handy while working.

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Challenges

#	File	Kahani	Data Type & Methods	Points
01	01-aadhaar-masker.js	Aadhaar Number Masker	Strings: slice, repeat, length, padStart	7
02	02-chai-dukaan-menu.js	Raju ki Chai Dukaan Menu	Arrays: Array.isArray, filter, map, join	7
03	03-bollywood-title-fixer.js	Bollywood Title Fixer	Strings: trim, split, map, join, charAt, toUpperCase, toLowerCase	8
04	04-gst-calculator.js	GST Calculator	Numbers: toFixed, parseFloat, Number.isFinite, Math.round	8
05	05-mumbai-local-pass.js	Mumbai Local Train Pass	Strings+Objects: template literals, slice, toUpperCase, typeof	8
06	06-whatsapp-parser.js	WhatsApp Message Parser	Strings: indexOf, substring, slice, includes, split, trim	9
07	07-school-report-card.js	School Report Card	Objects+Numbers: Object.keys/values/entries, reduce, filter, toFixed	9
08	08-ipl-auction-purse.js	IPL Auction Purse Manager	Arrays+Objects: reduce, filter, sort, find, every, some	8
09	09-zomato-order-builder.js	Zomato Order Builder	Mixed: map, reduce, split, parseFloat, Math.max, Math.min	9
10	10-upi-transaction-log.js	UPI Transaction Log	Mixed: filter, reduce, sort, every, some, Object.entries	9
11	11-jugaad-form-validator.js	Jugaad Form Validator	Type coercion: typeof, Boolean(), parseInt, isNaN, ?., ??	9
12	12-railway-pnr-system.js	Railway PNR Status	All types: padEnd, slice, map, every, some, template literals	9

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Submitting Your Work

1. Check your progress

Run all tests to see how many you've solved:

npm test

2. Stage your changes

git add src/

Important: Only add files from src/. Do not modify or commit test files.

3. Commit your work

git commit -m "Complete datatypes lab"

You can commit as many times as you want — each push triggers a new grading run.

4. Push to GitHub

git push origin main

5. Check your grade

After pushing, go to your repository on GitHub:

1. Click the Actions tab
2. You'll see a workflow run in progress (or completed)
3. Click on it to see which tests passed and your total score out of 100

You can push again to improve your score — GitHub Classroom will always use the latest result.

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Tips for Success

• JSDoc dhyan se padho — every rule and edge case is described there
• Built-in methods use karo — har challenge mein hint diya hai kaunse methods kaam aayenge
• typeof check karo — validation mein typeof bahut important hai
• Return types dhyan se dekho — kuch functions objects return karte hain, kuch strings, kuch null
• Don't modify the test files — only edit files in src/
• Commit often — don't wait until you've solved everything to push
• Use console.log() — add temporary logs to debug, then remove them before submitting

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Concepts Covered

• Strings: length, charAt, indexOf, includes, startsWith, endsWith, slice, substring, split, join, replace, toUpperCase, toLowerCase, trim, repeat, padStart, padEnd, template literals
• Numbers: toFixed, parseInt, parseFloat, isNaN, Number.isFinite, Number.isInteger, Math.round, Math.max, Math.min, Math.abs
• Booleans & Type Coercion: typeof, truthy/falsy values, Boolean(), Number(), String(), implicit coercion
• Arrays: Array.isArray, length, map, filter, reduce, find, findIndex, every, some, sort, join, flat, concat, forEach
• Objects: Object.keys, Object.values, Object.entries, Object.assign, spread operator, destructuring
• null/undefined: typeof null quirk, nullish coalescing (??), optional chaining (?.), default values
• Input validation and edge case handling

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Troubleshooting

Problem	Solution
npm test shows "command not found"	Run npm install first
npm test fails on Windows	Use npm run test:win instead
All tests fail with undefined	You haven't written your solution yet — that's expected
Tests say "expected X but received Y"	Your logic is close but not matching the rules — re-read the JSDoc
git push is rejected	Run git pull origin main first, then push again
Tests pass locally but fail on GitHub	Make sure you pushed all your changes (git status to check)

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Good luck! Aur haan, built-in methods ka MDN documentation khul ke rakho!