Hallucinated API

.flatten(), .contains(), .substr() — methods AI invents

warningAI Qualityhallucinated-api

Why this matters

AI tools confidently use methods that don't exist in the runtime you're targeting. .flatten() instead of .flat(), .contains() instead of .includes(), or methods from different languages entirely.

✗ Bad

const nested = [[1, 2], [3, 4]];
const flat = nested.flatten();

const hasAdmin = roles.contains("admin");

const prefix = name.substr(0, 3);

✓ Good

const nested = [[1, 2], [3, 4]];
const flat = nested.flat();

const hasAdmin = roles.includes("admin");

const prefix = name.slice(0, 3);

How to fix

Check MDN or TypeScript docs when a method call looks unfamiliar. Common AI hallucinations: .flatten()→.flat(), .contains()→.includes(), .substr()→.slice().

All rules