Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the logic errors pattern
The wrong operator, an inverted condition, a formula the right way round but backwards.
What went wrong: The in operator checks both the object and its entire prototype chain. Properties like toString and valueOf are inherited from Object.prototype.
The fix: Use Object.hasOwn() to check only direct own properties: Object.hasOwn(payload, fieldName)
Remember: In JavaScript, key in obj checks the prototype chain; use Object.hasOwn(obj, key) for own properties.
The pattern behind it: logic errors.
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<iframe src="https://trybughunt.com/embed/5c86d26e-8d0f-446f-aba9-b63ea3b71e3e" title="Debugging challenge: Checking property with in operator matches prototype methods" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe>
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