DebugMidFrontendAuto-graded
Fix a React counter that increments unpredictably
Auto-increment stops climbing after the first tick, and +1 doesn't reliably add one. Find out why and fix the component without rewriting it.Counter.jsx has a +1 button and an auto-increment toggle, and neither works as it should. Clicking +1 doesn't reliably add one, and auto-increment stops climbing after the first tick. Find out why and fix the existing component. Rewriting it from scratch isn't what's asked for.20 min
react, javascript
You're done when
- The counter goes up by exactly one per click and per tick, with no jumps.
- Auto-increment keeps adding one every second for as long as it's on, including after manual clicks.
- A single click on +1 adds exactly one.
- The fix is made in the existing component; it isn't rewritten.
What it measures
React stateHow you reason about what a component's state does as it changes.
DebuggingWhether you trace each symptom to its cause before changing code.
Small, focused fixWhether the change stays small enough for a reviewer to read in a minute.
Your environment
Terminal + editorA full shell in the browser
Claude CodePre-authenticated, no key setup
Isolated microVMYours alone, wiped afterwards
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