AI Prompts for Claude for JavaScript

Rewrite this older JavaScript code to use modern ES6+ features: [PASTE CODE]. Use arrow functions, destructuring, template literals, optional chaining, and nullish coalescing where they improve clarity.

Explain how [ASYNC/AWAIT / PROMISES / GENERATORS / MODULES] work in JavaScript with a concrete example I can run. Show the common mistakes people make and how to avoid them.

I keep confusing [DESCRIBE CONCEPT PAIR, E.G. "LET VS CONST VS VAR", "== VS ===", "NULL VS UNDEFINED VS NAN"]. Explain the real difference with examples that make it stick.

Write a utility function that [DESCRIBE BEHAVIOR]. Make it pure, handle edge cases, and write it in a way that is easy to test. Then write three unit tests for it.

What is the difference between [MAP/FILTER/REDUCE/FOREACH] and when should I use each? Show a real example where reduce is the right choice even though it looks more complex.

I have a race condition in this async code: [PASTE CODE]. Explain why it happens and rewrite it correctly.

Write a function that fetches data from [DESCRIBE API OR URL PATTERN] with proper error handling, a timeout, and a retry on failure. Use async/await.

What is Promise.all vs Promise.allSettled vs Promise.race vs Promise.any? Give me a real example where each one is the right choice.

I have callback hell in this code: [PASTE CODE]. Refactor it to use Promises and then to async/await. Show each step so I understand the progression.

How do I run [N] async operations concurrently but limit the maximum concurrency to [N] at a time? Write the implementation.

Write a Node.js script that [DESCRIBE TASK, E.G. "READS A CSV, TRANSFORMS IT, AND WRITES JSON"]. Include error handling and make it run correctly from the command line.

Set up an Express.js API with these routes: [DESCRIBE ROUTES]. Include input validation, error handling middleware, and a consistent response format.

I need to read and write files asynchronously in Node.js: [DESCRIBE TASK]. Write the code using the fs/promises API, handle the errors properly, and avoid blocking the event loop.

How do I handle environment variables in a Node.js project correctly? Show me the setup that works for local development, CI, and production without committing secrets.

Explain the Node.js event loop to me with a concrete example. Why does this code behave unexpectedly: [PASTE CODE SHOWING EVENT LOOP CONFUSION]?

I have a bug I cannot find: [DESCRIBE WHAT SHOULD HAPPEN VS WHAT IS HAPPENING, PASTE RELEVANT CODE]. Walk me through diagnosing this step by step.

Review this JavaScript function for bugs, edge cases, and readability issues: [PASTE FUNCTION]. Rewrite it with your improvements and explain each change.

My code works but it is hard to read and maintain: [PASTE CODE]. Refactor it for clarity — better naming, smaller functions, less nesting — without changing the behavior.

I need to add error handling to this code: [PASTE CODE]. Show me where errors can occur, how to catch them at the right level, and how to give helpful error messages.

Set up ESLint and Prettier for this project. What rules should I start with and how do I configure them to enforce the style rules that matter most?