| # | title | topic | type | difficulty |
|---|---|---|---|---|
| 1 | Spot the anti-pattern: == everywhere | Patterns & Performance | Multiple choice | Easy |
| 2 | Spot the anti-pattern: var in 2026 | Patterns & Performance | Multiple choice | Easy |
| 3 | Copy or alias? | Patterns & Performance | Multiple choice | Easy |
| 4 | The accidentally quadratic accumulator | Patterns & Performance | Multiple choice | Medium |
| 5 |
| Kill the O(n²) lookup |
| Patterns & Performance |
| Coding |
| Medium |
| 6 | Plain object or Map? | Patterns & Performance | Multiple choice | Medium |
| 7 | Hidden classes: the shape game | Patterns & Performance | Multiple choice | Hard |
| 8 | Four duplicates checks, one is optimal | Patterns & Performance | Multiple choice | Hard |
| 9 | Order-preserving dedupe at scale | Patterns & Performance | Coding | Hard |
| 10 | The lazy singleton pattern | Patterns & Performance | Coding | Hard |
| 11 | Observer pattern with unsubscribe | Patterns & Performance | Coding | Medium |
| 12 | Prototype pattern: share the methods | Patterns & Performance | Coding | Medium |
| 13 | Mixin pattern: compose behaviors | Patterns & Performance | Coding | Medium |
| 14 | Factory functions vs constructors | Patterns & Performance | Multiple choice | Easy |