JavaScript Loops Lab

Master JavaScript loops through 12 desi, story-based challenges! From Raju ki chai tapri to IRCTC tatkal booking, each problem puts you in a real Indian scenario where you need to write the logic using for, while, do...while, for...of, and nested loops.

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-loops-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.

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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-chai-tapri.js and work your way up.

src/
├── 01-chai-tapri.js          ← Start here
├── 02-cricket-scoreboard.js
├── 03-auto-rickshaw-meter.js
├── 04-bollywood-playlist.js
├── 05-sabzi-mandi.js
├── 06-diwali-lights.js
├── 07-ipl-points-table.js
├── 08-emi-calculator.js
├── 09-upi-retry.js
├── 10-biryani-order.js
├── 11-rangoli-pattern.js
└── 12-indian-railways.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

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 chaiTapriRevenue(customers) {
  // Your code here
}

// After (example)
export function chaiTapriRevenue(customers) {
  if (!Number.isInteger(customers) || customers <= 0) {
    return { totalChai: 0, totalRevenue: 0 };
  }

  let totalRevenue = 0;
  for (let i = 1; i <= customers; i++) {
    // ... your logic
  }
  return { totalChai: customers, totalRevenue };
}

Step 4 — Run the test for that challenge

npm test -- 01-chai

You can use any part of the filename to match:

npm test -- 02-cricket
npm test -- 03-auto
npm test -- bollywood
npm test -- sabzi
npm test -- biryani

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	Loop Concept	Points
01	01-chai-tapri.js	Raju ki Chai Tapri	Basic for loop, modulo, accumulator	7
02	02-cricket-scoreboard.js	Gully Cricket Scoreboard	for loop, break, multiple counters	7
03	03-auto-rickshaw-meter.js	Pappu ka Auto Meter	while loop, rate tiers, Math.ceil	8
04	04-bollywood-playlist.js	Simran ki Road Trip Playlist	while with lookahead, skip invalid	8
05	05-sabzi-mandi.js	Amma ki Sabzi Mandi	for...of, object lookup, array building	8
06	06-diwali-lights.js	Sharma ji ki Diwali Lights	for...of + while trim, budget constraint	8
07	07-ipl-points-table.js	IPL Season Points Table	for with object accumulator, sorting	9
08	08-emi-calculator.js	Rohit ka Phone EMI	while accumulator, infinite loop guard	9
09	09-upi-retry.js	Bunty ka UPI Retry	do...while, exponential backoff	8
10	10-biryani-order.js	Paradise Biryani Batches	do...while with state, queue processing	8
11	11-rangoli-pattern.js	Priya ki Diwali Rangoli	Nested for loops, diamond pattern	10
12	12-indian-railways.js	IRCTC Tatkal Reservation	Nested loops, multi-pass, mutation	10

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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 loops 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
• Boundary values check karo — tests often check exact boundaries
• Loop type matters — some problems specifically need for, while, do...while, or for...of
• Return types matter — most functions return objects, check the exact shape
• 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

• for loops with counters and accumulators
• while loops with dynamic conditions
• do...while loops (execute at least once)
• for...of loops for iterating arrays
• break statement to exit loops early
• Nested loops for complex patterns
• Object accumulators (building objects in loops)
• Array building within loops
• Math.ceil() for rounding up
• Exponential backoff pattern
• Input validation and edge cases

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Troubleshooting

Problem	Solution
npm test shows "command not found"	Run npm install first
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, chai peete peete code karna!