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You will get stuck. That’s normal.

Every developer — beginner and senior — gets stuck regularly. The difference isn’t whether you get stuck, it’s knowing where to look and how to ask. Here’s your toolkit.

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Where to look first

Before asking anyone, try these in order:
1

Read the error message

JavaScript error messages are usually clear. Cannot read properties of undefined (reading 'name') means something is undefined when you expected an object. Read the message, check the line number.
2

Check the browser DevTools

Console tab for JavaScript errors. Network tab for API request/response issues. Elements tab for what’s actually rendered.
3

console.log() the data

Add console.log(data) before the line that breaks. Check if the data is what you expect. This solves 80% of bugs.
4

Search the error message

Copy the error message (without your specific file paths) and paste it into Google. Chances are someone has already solved this exact problem.
When you Google an error, add the technology name. “Cannot read properties of undefined React” gets better results than just the error message alone.

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Where to ask questions

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Stack Overflow

The largest Q&A site for developers. Search first — your question has almost certainly been asked before. When asking a new question:
  • Include the error message (exact text)
  • Include the relevant code (minimal reproduction)
  • Describe what you expected vs what happened
  • Mention what you’ve already tried

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MDN Web Docs

Not just a reference — MDN has explanations, examples, and browser compatibility tables for every JavaScript feature. When you’re confused about how something works, MDN is the answer.

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React docs

The new React docs at react.dev have interactive examples you can edit and run directly in the browser. If you’re confused about a React concept, the docs probably have a tutorial for it.

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Asking good questions

The quality of help you get depends on the quality of your question. Here’s the formula: 
1. What I'm trying to do:       "I'm trying to fetch users and display them in a list"
2. What I expected to happen:    "The list should show 3 users from the API"
3. What actually happened:       "The page shows 'Loading...' forever"
4. The error message (if any):   "No errors in the console"
5. What I already tried:         "I checked the Network tab — the API returns 200 with data"
6. Relevant code:                [minimal code snippet]
A question like this gets answered quickly. “My code doesn’t work, help” does not.
Creating a minimal reproduction is the most valuable debugging skill you can develop. Often, the act of simplifying the problem to its essentials reveals the bug — and you solve it yourself before even asking.

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Reference documentation

Bookmark these. You’ll come back to them constantly.
ResourceWhat it covers
MDN Web DocsJavaScript, DOM, Web APIs, CSS
react.devReact components, hooks, patterns
fastapi.tiangolo.comFastAPI endpoints, validation, middleware
vitejs.devVite configuration, environment variables, building
developer.chrome.com/docs/devtoolsChrome DevTools guides

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Common problems and where to look

ProblemWhere to check
”Cannot read properties of undefined”Your data isn’t what you think — console.log it
CORS error in consoleBackend CORS middleware configuration
API returns 422Your request body doesn’t match the Pydantic model
Component doesn’t re-renderYou might be mutating state instead of creating new objects
useEffect runs infinitelyCheck your dependency array for objects/arrays
Form input won’t typeMissing onChange handler on a controlled input
”Module not found”Check your import path — relative (./) and case sensitivity
key warning in consoleAdd a unique key prop to items in .map()

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Contributing to this course

Found a typo? Want to suggest an improvement? This course is open source.
  • Report issues: Open a GitHub issue describing the problem
  • Suggest improvements: Pull requests are welcome
  • Share feedback: Let us know what helped and what was confusing

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Keep going

You’ve completed the course. You have the foundation. The rest is practice and curiosity. Build something this week. It doesn’t have to be perfect — it has to exist. Every project you build makes you better. Every bug you fix teaches you something new. Welcome to full-stack development.