Errors & Debugging

Every one of these started as an error message someone pasted into a search box at 1am. Each article explains what the message actually means, why your code produced it, and the fix — plus how to avoid the same class of bug next time.

35 articles

JavaScript and Node errors

JavaScript Error Handling: try, catch and Async Traps A try/catch around code that returns a promise catches nothing. The catch block has already finished by the time the failure arrives, and the error escapes silently. Tutorial · 12 min read · August 6, 2026
Python TypeError: Five Patterns and Their Real Causes Most TypeErrors are not about types at all. They are about a variable holding something you never intended to put there, one or two lines earlier. Tutorial · 11 min read · August 6, 2026
EADDRINUSE: Port Already in Use and How to Fix It The process holding port 3000 is almost always your own server from ten minutes ago. Killing it blindly is the wrong habit; finding it takes one command. Tutorial · 11 min read · August 6, 2026
SyntaxError: Unexpected Token and How to Locate It The line number in a SyntaxError is almost never the line with the mistake. And when the unexpected token is a less-than sign, your API returned an HTML error page. Tutorial · 11 min read · August 6, 2026
Module Not Found: Fixing Cannot Resolve Errors The import works on your Windows laptop and fails on the Linux deploy box. That is not a mystery; it is your filesystem quietly ignoring capital letters. Tutorial · 11 min read · August 6, 2026
Cannot GET /: Fixing Express Route Errors Cannot GET / is not an error at all. It is proof your server started perfectly and simply has no handler for that path, which means the fix is never in listen(). Tutorial · 11 min read · August 6, 2026
Unhandled Promise Rejection in Node: Causes and Fixes One missing await turns a try/catch into decoration. The block completes, the promise rejects a moment later, and modern Node responds by killing your server. Tutorial · 11 min read · August 6, 2026
Why Your JavaScript Says NaN (and How to Fix It) NaN is contagious — one appears and every calculation downstream becomes NaN. Finding the first one is the entire debugging task. Tutorial · 8 min read · August 6, 2026
Maximum Call Stack Size Exceeded: Causes and Fixes A stack overflow in JavaScript. Usually a missing base case — but the React version and the accidental-recursion version are sneakier. Tutorial · 9 min read · August 6, 2026
How to Debug a 500 Internal Server Error A 500 tells you nothing except that the server failed. The logs tell you everything — and most people never look at them. Tutorial · 10 min read · August 6, 2026
TypeError: Cannot Read Property of Undefined — How to Fix It The most common error in JavaScript, and the message points at the symptom rather than the cause. Here is how to find where the undefined actually came from. Tutorial · 9 min read · August 6, 2026
npm Errors Explained: ERESOLVE, EACCES, ENOENT and More npm errors look alarming and are mostly four recurring problems. Knowing which one you have turns a lost afternoon into a two-minute fix. Tutorial · 10 min read · August 6, 2026
What Is CORS and How to Fix the Error The request worked in Postman and fails in the browser. Nothing is broken — you are meeting a rule that only browsers enforce. Tutorial · 10 min read · August 5, 2026

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