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March 8, 2026 • 3 min read

When the Code Works But You Don’t Know Why

Table of Contents

  • • The Unofficial Rule
  • • The React State Trap
  • • The Cost of "Mystery Fixes"
  • • Building a Mental Model

Every developer eventually reaches a very specific moment in their journey. A moment that feels both victorious and slightly terrifying.

The code finally works.

The program runs. The output is correct. The bug is gone. Everything behaves exactly as expected. And yet… you have absolutely no idea why.

This usually happens after a long debugging session where logic slowly collapses into chaos. At some point you start changing random things just to see what happens. You rename variables, move a line of code, add a console.log, remove a bracket, reinstall dependencies, restart the dev server, sacrifice a rubber duck to the debugging gods… and suddenly the program works.

You stare at the screen. It works. But the deeper question appears immediately: Why does it work?

The Unofficial Rule

Many developers have experienced this exact situation. In fact, there’s an unofficial rule in programming that says if you don’t understand why the code works, it will break again later.

A classic example appears with asynchronous JavaScript. A developer writes something like this:

fetchData();
processData();

But processData() runs before fetchData() finishes, so the program breaks. After some experimentation, the developer changes the code to this:

await fetchData();
processData();

The bug disappears. Everything works now. But if the developer doesn’t understand why await fixed the problem, the same mistake will appear again in another part of the codebase.

The React State Trap

Another common example happens with React state updates. A developer changes something like this:

setCount(count + 1);
setCount(count + 1);

But the count only increases by 1 instead of 2. After reading a few posts, they change it to:

setCount(prev => prev + 1);
setCount(prev => prev + 1);

The issue disappears. But again, if the reasoning behind it is unclear, the fix becomes a lucky accident instead of real understanding.

The Cost of "Mystery Fixes"

This is the dangerous part of “mystery fixes.” When developers accept a working solution without understanding the cause, the codebase slowly fills with fragile logic. The program becomes a strange collection of lines that nobody wants to touch anymore.

You’ll hear sentences like:

  • “Don’t change that function.”
  • “It breaks everything.”
  • “I don’t know why it works, but it works.”

At that point, the code has become a haunted house.

Building a Mental Model

Experienced developers treat these moments differently. When something suddenly starts working, they pause and investigate. They ask questions like:

  • What exactly changed?
  • What behavior did this line modify?
  • What assumption about the system was incorrect before?

Sometimes the answer reveals a deeper concept about the language or framework. Sometimes it exposes a misunderstanding about how data flows through the system. That moment of understanding is where real learning happens.

Programming is not just about getting the correct output. It is about building a mental model of how the system behaves. When you know why the code works, you gain something much more valuable than a passing test case. You gain a tool that can be applied to future problems.

Because in programming, mysterious fixes have a habit of coming back later. Usually at 2 AM.

And they never arrive alone.