Choose Your Level
Pick the difficulty that matches where you are. You can come back and try a harder level later.
Beginner
Fix a Bug in a Sample To-Do App
Diagnose and fix a state management bug in a React to-do app.
1 to 2 hours 4 criteria
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Intermediate
Memory Leak in an Event Listener
Diagnose and fix a React memory leak caused by un-garbage-collected DOM nodes.
2 to 3 hours 3 criteria
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Advanced
Race Condition in Async Data Fetching
Fix a tricky race condition where stale network responses overwrite fresh data.
3 to 4 hours 3 criteria
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