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Curated lists of coding questions, ranging from Javascript, React, Node, Web Development. Perfect for your daily coding practice.

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Beginner Questions

Learn the basics of programming with these beginner questions.

You are writing your first JavaScript program to greet users. Fill in the blank to make this code work:

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Beginner

You are trying to create a while loop that will increase the petCount to 5. Why is this solution not working?

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Beginner

During a code review, you spot this comparison in a payment processing function. What potential issue exists in this code?

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Beginner

You're building a task management system and need to manipulate a list of tasks. What's incorrect about this implementation?

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Beginner

What will be the value of value after these lines execute?

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Beginner

What will this code output?

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Beginner

String concatenation

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Getting the length of an array

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If statements in JavaScript

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Beginner

Javascript Questions

Learn how to use JavaScript to build more efficient and scalable applications.

React Questions

Explore the most popular JavaScript framework, React.

React Hooks

Learn how to use React Hooks to build more efficient and scalable applications.

Arrays

Learn all the key concepts of arrays in JavaScript.

Asynchronous Programming

Learn how to handle asynchronous operations in JavaScript.

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Explore Questions

Beginner Questions

You are writing your first JavaScript program to greet users. Fill in the blank to make this code work:

You are trying to create a while loop that will increase the petCount to 5. Why is this solution not working?

During a code review, you spot this comparison in a payment processing function. What potential issue exists in this code?

You're building a task management system and need to manipulate a list of tasks. What's incorrect about this implementation?

What will be the value of value after these lines execute?

What will this code output?

String concatenation

Getting the length of an array

If statements in JavaScript

Javascript Questions

React Questions

React Hooks

Arrays

Asynchronous Programming

Javascript Questions

React Questions

React Hooks

Arrays

Asynchronous Programming

How would you complete this function to implement a retry mechanism with exponential backoff for failed API calls?

What's the correct implementation to create a reactive object that logs all property access and modifications?

What's missing in this custom iterator implementation that uses generators to process a large dataset in chunks?

Complete the WebSocket manager to implement automatic reconnection with backoff:

What's the correct implementation for this simplified virtual DOM diffing algorithm?

What code is missing to implement a memory leak detector that monitors DOM mutations?

Implement the missing transition logic in this state machine:

Dynamic Product Sorting Implementation

Internationalization-Aware String Sorting

Semantic Version Sorting Algorithm

What's missing in this custom iterator implementation that uses generators to process a large dataset in chunks?

In a social media app, you need to implement a feature that processes user comments. What will the output be when this code runs?

You're developing an e-commerce checkout system that needs to process multiple discount codes. What's wrong with this implementation?

You're building a content filtering system. What will this code output when processing user-generated content?

You're debugging a financial dashboard where transaction totals aren't updating correctly. The code processes multiple currency conversions asynchronously. What's the fundamental issue with this implementation?

You're building a social media dashboard that needs to process user engagement data. Given an array of post interactions, which method chain would correctly calculate the average engagement rate (likes + comments / total posts) for posts with more than 100 views?

Complete the missing code to transform an array of user records into a structured report:

Dynamic Product Sorting Implementation

Internationalization-Aware String Sorting

Semantic Version Sorting Algorithm

You are processing user data for an e-commerce platform. Each user has a list of orders, and you need to find the first active user over the age of 30 who has made at least one order. Which line of code completes the following snippet?

You're building a React component for a weather dashboard. Which implementation correctly updates the temperature display?

When building a music streaming app, you notice user actions (like seeking in a track) are causing too many API calls. How would you optimize the custom hook below to reduce server load while maintaining a smooth user experience?

While building a content management system, your team needs to implement a document autosave feature. What's missing from this code to prevent excessive save operations?

In this e-commerce product list component, what's causing unnecessary re-renders and how would you fix it?

Complete the missing code in this custom form validation hook:

What's the optimal way to implement the missing parts of this theme provider?

Why isn't the cart count updating immediately in this component?

Complete the missing code to make this controlled form component work:

You're building a modal component that needs to render outside the main app container. Why is this implementation causing the modal to disappear unexpectedly?

Complete the state update logic for this sortable list component:

In an e-commerce product catalog, you need to implement a search feature that highlights matching terms. Which approach fixes the performance issue in this code?

When building a music streaming app, you notice user actions (like seeking in a track) are causing too many API calls. How would you optimize the custom hook below to reduce server load while maintaining a smooth user experience?

In a React e-commerce application, you need to implement a shopping cart hook that persists across page refreshes. What's wrong with this custom hook implementation?

You're building a React data visualization component that needs to efficiently update when its data changes. Why might this implementation cause performance issues?

In this e-commerce product list component, what's causing unnecessary re-renders and how would you fix it?

Complete the missing code in this custom form validation hook:

What's the optimal way to implement the missing parts of this theme provider?

Why isn't the cart count updating immediately in this component?

Complete the missing code to make this controlled form component work:

You're building a modal component that needs to render outside the main app container. Why is this implementation causing the modal to disappear unexpectedly?

In JavaScript, when working with Promises, what is a practical use case for Promise.all?

Which statement is true about async functions and their returned values?

How can you ensure that an array of promises resolves in sequence instead of in parallel?

What will this code output and why?

You're implementing a caching system for expensive calculations in a web application. The cache should automatically clear old entries to prevent memory leaks. What's missing in this implementation?

You're developing an e-commerce checkout system that needs to process multiple discount codes. What's wrong with this implementation?

You're debugging a financial dashboard where transaction totals aren't updating correctly. The code processes multiple currency conversions asynchronously. What's the fundamental issue with this implementation?

Which statement is true about async functions and their returned values?

How can you ensure that an array of promises resolves in sequence instead of in parallel?

What will this code output and why?

How would you dynamically import a module in JavaScript only when it is needed?

You're developing an e-commerce checkout system that needs to process multiple discount codes. What's wrong with this implementation?

How would you complete this function to implement a retry mechanism with exponential backoff for failed API calls?

What's missing in this custom iterator implementation that uses generators to process a large dataset in chunks?