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mohammadAli
mohammadAli

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A Small React Bug That Taught Me to Debug the Render Chain

#debugging #nextjs #react #typescript

Debugging a Small React Rendering Bug in FocusYar

While building the Task section of my Next.js project, FocusYar, I ran into a simple problem:

I clicked the Edit button, but the EditTask component didn't appear.

At first, I looked at the component itself and the Todo data. But the actual problem was much simpler.

The Problem

The component was rendered conditionally:

{openDetailTsk === detail.id && afterEditDetailTask && (
  <EditTask />
)}
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I was updating:

setopenDetailTsk(id);
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but I wasn't updating:

afterEditDetailTask
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So even though the first condition became true, the second one remained false.

As a result, React correctly didn't render the component.

The fix was simply to update both states:

setopenDetailTsk(id);
setAfterEditDetailTask(true);
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Another TypeScript Lesson

I also encountered a TypeScript event type mismatch.

The handler was attached to a button:

<button onClick={...}>
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but I had typed the event as:

React.MouseEvent<HTMLDivElement>
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Since the event came from a <button>, the correct type was:

React.MouseEvent<HTMLButtonElement>
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This was a good reminder that TypeScript can help us understand exactly which DOM element we're working with.

One More Thing I Learned

During this process, I initially thought I needed to get all Todos and use find() to locate the task I wanted to edit.

But then I realized I already had the current Todo in detail.

So instead of unnecessarily getting the data again:

all Todos
   ↓
find()
   ↓
selected Todo
   ↓
EditTask
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I could simply use the data I already had:

detail
   ↓
EditTask
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This made the data flow simpler and avoided an unnecessary step.

My Debugging Checklist

When a React component doesn't appear, I now try to follow the rendering chain step by step:

Click
  ↓
Event handler
  ↓
State update
  ↓
Render condition
  ↓
Props
  ↓
Component
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This small bug was a useful reminder:

Don't debug only the component. Debug the whole rendering chain.

And the best part?

I eventually found and fixed the bug myself. 🚀

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