| # | title | topic | type | difficulty |
|---|---|---|---|---|
| 1 | Array.prototype.at is generic | Arrays | Multiple choice | Hard |
| 2 | Sparse arrays and holes | Arrays | Multiple choice | Hard |
| 3 | The + operator: string context wins | Type Coercion | Multiple choice | Hard |
| 4 | The == algorithm, step by step | Type Coercion | Multiple choice | Hard |
| 5 | What Object.groupBy actually returns |
| Objects |
| Multiple choice |
| Hard |
| 6 | Relative URL resolution | URL & Web APIs | Multiple choice | Hard |
| 7 | Which sink executes? | Security | Multiple choice | Hard |
| 8 | IEEE 754 quirks | Floating Point | Multiple choice | Hard |
| 9 | has trap + Reflect + invariants | Proxy & Reflect | Multiple choice | Hard |
| 10 | What 'use strict' actually changes | Strict Mode | Multiple choice | Hard |
| 11 | The four this-binding rules, in precedence order | YDKJS Book | Multiple choice | Hard |
| 12 | [] == ![] | WTF Quirks | Multiple choice | Hard |
| 13 | Generators talk back | Quiz: JS Questions | Multiple choice | Hard |
| 14 | null >= 0 but null != 0 | Type Coercion | Multiple choice | Hard |
| 15 | The army of things equal to nothing | Type Coercion | Multiple choice | Hard |
| 16 | '10' < '9' — string comparison traps | Type Coercion | Multiple choice | Hard |
| 17 | {} + [] — position is everything | Type Coercion | Multiple choice | Hard |
| 18 | Symbols: explicit yes, implicit never | Type Coercion | Multiple choice | Hard |
| 19 | Loose equality is not transitive | Type Coercion | Multiple choice | Hard |
| 20 | Hidden classes: the shape game | Patterns & Performance | Multiple choice | Hard |
| 21 | Four duplicates checks, one is optimal | Patterns & Performance | Multiple choice | Hard |
| 22 | What triggers a CORS preflight? | Web Platform | Multiple choice | Hard |
| 23 | no-cache does not mean no cache | Web Platform | Multiple choice | Hard |
| 24 | Microtask starvation | Event Loop & Memory | Multiple choice | Hard |
| 25 | Find the leak-proof cache | Event Loop & Memory | Multiple choice | Hard |
| 26 | typeof is not always safe | Scope & Hoisting | Multiple choice | Hard |
| 27 | The name only it can see | Scope & Hoisting | Multiple choice | Hard |
| 28 | const meets the classic for loop | Scope & Hoisting | Multiple choice | Hard |
| 29 | The event that refuses to bubble | DOM Events | Multiple choice | Hard |
| 30 | The removal that silently fails | DOM Events | Multiple choice | Hard |