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Quiz Application

Interactive quizzes with timers, scoring and results.

~10 hours 6 phases
JavaScriptHTMLCSS

Overview

Build a quiz application with multiple-choice questions, a per-question timer, scoring, a results screen and reusable question components. Learn state management, timers and result handling.

The problem

Deliver an interactive quiz with timed questions, scoring, results and reusable question components.

Why it matters

Interactive, stateful UIs are the core of most frontend work; this proves you can manage complex UI state cleanly.

What you'll build

  • A timed multiple-choice quiz
  • Score tracking
  • Results screen
  • Restart flow

What you'll learn

  • State management
  • Timer handling with cleanup
  • Component reuse
  • Conditional rendering

Business problem

Users need an engaging, timed quiz that tracks progress and delivers a meaningful result.

Technical problem

Coordinate question flow, timing, scoring and results in a clean, reusable structure.

When you're done: A polished, timed quiz application with accurate scoring and results.

Requirements

User requirements

  • Answer multiple-choice questions
  • See a countdown timer
  • Get a score and result
  • Restart the quiz

System requirements

  • Timer per question
  • Accurate scoring

Functional requirements

  • Question navigation
  • Per-question timer
  • Answer selection
  • Score and results screen
  • Restart

Non-functional requirements

  • Clear state transitions
  • Keyboard accessible answers
  • Responsive

Technical requirements

  • Central state for the quiz session
  • Timer management with cleanup
  • Reusable QuestionCard

Security requirements

  • No user data stored beyond session

Operational requirements

  • Works offline from static deploy

Constraints

  • Frontend only
  • Static question bank

Success criteria

  • Timer works correctly
  • Score is accurate
  • Results explain performance

Flows

Request Flow

  1. 1

    Browser

    User requests the application over HTTPS.

  2. 2

    CDN / DNS

    Edge routes the request to the origin.

  3. 3

    Load Balancer

    Distributes traffic across healthy app instances.

  4. 4

    Application

    Handles the request, applies business logic.

  5. 5

    Cache

    Serves fast reads for hot data.

  6. 6

    Database

    Persists data and returns results.

Project Structure

Root of the client application source.

Setup

  1. 1

    Prerequisites

    You need the tools required by JavaScript, HTML, CSS installed and available on your PATH.

  2. 2

    Clone project

    Clone the repository locally.

    1. Clone the repository
    git clone <your-repo-url> <project-folder>
  3. 3

    Install dependencies

    Install the project dependencies.

    1. Initialize a Node.js project
    npm init -y

    Expected

    Creates a package.json with defaults.

    If it fails

    command not found: npm

    Fix

    Install Node.js LTS from the official site, then reopen your terminal.

  4. 4

    Configure environment

    Set the environment variables documented for this project. Never commit secrets.

    1. Create the environment file
    cp .env.example .env   # then edit values
  5. 5

    Start project

    Run the development command and confirm it starts.

    1. Start the development server
    npm run dev

    Expected

    Dev server starts; watch terminal for the local URL.

    If it fails

    Port 3000 is already in use

    Fix

    Run on another port: npm run dev -- --port 3001, or stop the conflicting process.

  6. 6

    Verify

    Open the printed local URL and confirm the primary flow works.

Build Phases

0 of 6 phases complete

  1. Objective: Establish the next milestone of the client-side interface.

    What changes: The project advances to the next coherent state, keeping the previous milestones working.

    Files touched

    Relevant source and configuration files for this milestone.

    Run

    1. Initialize a Node.js project
    npm init -y

    Expected

    Creates a package.json with defaults.

    If it fails

    command not found: npm

    Fix

    Install Node.js LTS from the official site, then reopen your terminal.

    Tasks

    • Implement the specific behaviour required for this milestone.
    • Verify the previous milestone still works.

    Validate: The milestone behaves as expected and does not break existing functionality.

    Common mistakes

    • • Skipping validation and moving on before confirming the milestone works.

  2. Objective: Establish the next milestone of the client-side interface.

    What changes: The project advances to the next coherent state, keeping the previous milestones working.

    Files touched

    Relevant source and configuration files for this milestone.

    Run

    1. Install the javascript package
    npm install javascript

    Expected

    Adds javascript to node_modules and package.json.

    If it fails

    npm ERR! network / EACCES

    Fix

    Check your network or run with sudo on Linux/macOS; on Windows run the terminal as Administrator.

    Tasks

    • Implement the specific behaviour required for this milestone.
    • Verify the previous milestone still works.

    Validate: The milestone behaves as expected and does not break existing functionality.

    Common mistakes

    • • Skipping validation and moving on before confirming the milestone works.

  3. Objective: Establish the next milestone of the client-side interface.

    What changes: The project advances to the next coherent state, keeping the previous milestones working.

    Files touched

    Relevant source and configuration files for this milestone.

    Run

    1. Start the development server
    npm run dev

    Expected

    Dev server starts; watch terminal for the local URL.

    If it fails

    Port 3000 is already in use

    Fix

    Run on another port: npm run dev -- --port 3001, or stop the conflicting process.

    Tasks

    • Implement the specific behaviour required for this milestone.
    • Verify the previous milestone still works.

    Validate: The milestone behaves as expected and does not break existing functionality.

    Common mistakes

    • • Skipping validation and moving on before confirming the milestone works.

  4. Objective: Establish the next milestone of the client-side interface.

    What changes: The project advances to the next coherent state, keeping the previous milestones working.

    Files touched

    Relevant source and configuration files for this milestone.

    Run

    1. Build the application for production
    npm run build

    Expected

    A production bundle is emitted to the output directory.

    If it fails

    Build fails with a type or syntax error

    Fix

    Read the error message, fix the referenced file, and re-run the build.

    Tasks

    • Implement the specific behaviour required for this milestone.
    • Verify the previous milestone still works.

    Validate: The milestone behaves as expected and does not break existing functionality.

    Common mistakes

    • • Skipping validation and moving on before confirming the milestone works.

  5. Objective: Establish the next milestone of the client-side interface.

    What changes: The project advances to the next coherent state, keeping the previous milestones working.

    Files touched

    Relevant source and configuration files for this milestone.

    Tasks

    • Implement the specific behaviour required for this milestone.
    • Verify the previous milestone still works.

    Validate: The milestone behaves as expected and does not break existing functionality.

    Common mistakes

    • • Skipping validation and moving on before confirming the milestone works.

  6. Objective: Establish the next milestone of the client-side interface.

    What changes: The project advances to the next coherent state, keeping the previous milestones working.

    Files touched

    Relevant source and configuration files for this milestone.

    Tasks

    • Implement the specific behaviour required for this milestone.
    • Verify the previous milestone still works.

    Validate: The milestone behaves as expected and does not break existing functionality.

    Common mistakes

    • • Skipping validation and moving on before confirming the milestone works.

Commands

1. Initialize a Node.js project
npm init -y

Expected

Creates a package.json with defaults.

If it fails

command not found: npm

Fix

Install Node.js LTS from the official site, then reopen your terminal.

2. Install the javascript package
npm install javascript

Expected

Adds javascript to node_modules and package.json.

If it fails

npm ERR! network / EACCES

Fix

Check your network or run with sudo on Linux/macOS; on Windows run the terminal as Administrator.

3. Start the development server
npm run dev

Expected

Dev server starts; watch terminal for the local URL.

If it fails

Port 3000 is already in use

Fix

Run on another port: npm run dev -- --port 3001, or stop the conflicting process.

4. Build the application for production
npm run build

Expected

A production bundle is emitted to the output directory.

If it fails

Build fails with a type or syntax error

Fix

Read the error message, fix the referenced file, and re-run the build.

Testing

Unit tests

  • Core logic and pure functions behave correctly.

    npm init -y

    Success: All unit tests pass without errors.

Integration tests

  • Components integrate correctly with data sources and services.

    npm test

    Success: Integration tests pass for the primary flows.

API tests

  • Endpoints respond to valid and invalid input correctly.

    npm test

    Success: API tests cover happy and failure paths.

End-to-end tests

  • A user can complete the primary journey end to end.

    npm run test:e2e

    Success: The main user journey completes successfully.

Security tests

  • No obvious security regressions are introduced.

    npm audit

    Success: No high or critical vulnerabilities.

Debugging & Troubleshooting

Port already in use at startup

Why: Another process is binding the same port your app wants.

Check: List what is using the port.

lsof -i :3000   # Linux/macOS  |  netstat -ano | findstr :3000   # Windows

Fix: Free the port or start your app on a different port.

Prevent: Choose uncommon ports and document them in the README.

Environment variable missing or undefined

Why: A required value was not loaded into the runtime.

Check: Print the variable or inspect the config loader.

echo $MY_VAR   # Linux/macOS  |  echo %MY_VAR%   # Windows

Fix: Add the variable to your .env file and restart the process.

Prevent: Fail fast at startup when required env vars are absent.

API request times out

Why: An upstream call is slow or the network is blocked.

Check: Time a direct request against the upstream.

curl -w 'time_total: %{time_total}\n' http://upstream/health

Fix: Add timeouts and retries to the client; verify the upstream is up.

Prevent: Set explicit timeouts and circuit breakers on outbound calls.

Dependency fails to install or run

Why: Version conflicts or an incompatible runtime.

Check: Inspect the error and the installed versions.

npm ls <pkg>

Fix: Align versions or clear the lockfile and reinstall.

Prevent: Commit a lockfile and use the same Node version everywhere.

Security

Security is treated as a core requirement: input is validated, secrets are protected, and dependencies are kept up to date.

  • Input validation

    Validate and sanitize all user input before use.

  • Secrets management

    Store secrets in environment variables, never in source.

  • Dependency hygiene

    Regularly audit dependencies for known vulnerabilities.

Observability

Logs

  • Structured request logs with correlation IDs
  • Application-level error logs

Metrics

  • Request latency
  • Error rate
  • Throughput

Traces

  • Request tracing across the API and data layer

Health checks

  • A /health endpoint reporting readiness

Alerts

  • High error rate alert
  • Latency threshold alert

Dashboards

  • A dashboard showing requests, latency and errors

SLIs

  • Availability — Fraction of successful requests over the window
  • Latency — P95 response time

SLOs

  • Availability — 99.9% over 30 days
  • Latency — P95 under 500ms

Deployment

  1. 1

    Prepare for deployment

    Build the production artifact.

    1. Build for production
    npm run build
  2. 2

    Deploy

    Deploy to the project target platform following its documented steps.

    1. Deploy
    npm run deploy   # or the platform-specific command
  3. 3

    Verify

    Confirm the deployed application responds and its health check passes.

    1. Check health
    curl -I https://<your-deployed-url>

Documentation

Project Overview

Build a quiz application with multiple-choice questions, a per-question timer, scoring, a results screen and reusable question components. Learn state management, timers and result handling. This is a intermediate ui project in the client-side interface space, built to demonstrate real engineering, not just copied code.

What You Will Build

- A timed multiple-choice quiz - Score tracking - Results screen - Restart flow

Problem Statement

Users need an engaging, timed quiz that tracks progress and delivers a meaningful result. Coordinate question flow, timing, scoring and results in a clean, reusable structure.

Technology Stack

JavaScript, HTML, CSS

Installation

Clone the repository and install dependencies with the documented commands.

Local Development

Run the development command and open the printed local URL.

Testing

Run the test commands documented in the Testing section and confirm they pass.

Deployment

Follow the documented deployment steps for this project's target platform.

Interview Explanation

Use the Interview section to explain the architecture, technology choices and trade-offs.

Build Process

Phases guide the build in 6 checkpoints. Complete each and validate before moving on.

Interview Prep

30-second pitch

I built Quiz Application — deliver an interactive quiz with timed questions, scoring, results and reusable question components. It uses JavaScript, HTML, CSS and solves users need an engaging, timed quiz that tracks progress and delivers a meaningful result.

2-minute walkthrough

Build a quiz application with multiple-choice questions, a per-question timer, scoring, a results screen and reusable question components. Learn state management, timers and result handling. The core requirements were Question navigation, Per-question timer, Answer selection. I structured the work around Manage application state, Implement timers and intervals, Build reusable question components and validated the result with the documented tests.

Architecture

Because this is a frontend project, the architecture is concentrated in client-side interface rather than a distributed system.

Why these technologies

I chose JavaScript, HTML, CSS because they are the pragmatic, well-supported tools best suited to building a ui of this kind.

Why this architecture

The structure exists to keep concerns separated, make each piece testable, and scale the project cleanly as requirements grow.

At scale

At scale I would introduce caching, move to a service boundary structure, add proper observability, and enforce stricter contracts between components.

What can fail

The data source becomes unavailable, A dependency introduces a breaking change, Performance degrades under load, Configuration drift between environments

Monitoring

Monitoring is covered in the Observability section, focusing on requests, latency, errors and health checks.

Security

Security was handled by validating input, protecting secrets, and following the practices listed in the Security section.

Deployment strategy

Deployment follows the steps in the Deployment section for the target platform, with a health check to confirm success.

What I'd do differently

With more time I would add deeper test coverage, stronger observability, and automated deployment.

Practice Q&A

Why did you build Quiz Application?

To demonstrate Manage application state and Implement timers and intervals on a real, portfolio-worthy project.

What was the hardest part?

Coordinating the pieces so each stays correct as the project grows, and validating end to end.

How do you handle failure and scale?

By designing for correctness first and adding resilience once the core works.

Extensions

  • Add deeper test coverage
  • Add observability and alerting
  • Harden security
  • Automate deployment

Completion Checklist

Prerequisite Projects

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