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: String.prototype.substring() converts any negative argument to 0, returning the entire string from index 0.
The fix: Use String.prototype.slice() which properly supports negative offsets from the end: text.slice(-count)
Remember: In JavaScript, substring() treats negative values as 0; use slice() for negative offsets.
The pattern behind it: logic errors.
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<iframe src="https://trybughunt.com/embed/85c456cf-48d3-4cf0-9e8e-d19139deaf12" title="Debugging challenge: String substring with negative argument treats index as zero" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe>
<p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/85c456cf-48d3-4cf0-9e8e-d19139deaf12">TryBugHunt</a></p>