| # | title | topic | type | difficulty |
|---|---|---|---|---|
| 91 | typeof is not always safe | Scope & Hoisting | Multiple choice | Hard |
| 92 | The name only it can see | Scope & Hoisting | Multiple choice | Hard |
| 93 | const meets the classic for loop | Scope & Hoisting | Multiple choice | Hard |
| 94 | Event loop machine: microtasks cutting the line | Event Loop & Memory | Runtime machine | Hard |
| 95 |
| Hoisting machine: inside a function call |
| Scope & Hoisting |
| Runtime machine |
| Hard |
| 96 | Scope machine: one j, many i's | Scope & Hoisting | Runtime machine | Hard |
| 97 | The event that refuses to bubble | DOM Events | Multiple choice | Hard |
| 98 | The removal that silently fails | DOM Events | Multiple choice | Hard |
| 99 | The checkbox that un-checks itself | DOM Events | Multiple choice | Hard |
| 100 | passive listeners can't say no | DOM Events | Multiple choice | Hard |
| 101 | Editing the guest list mid-party | DOM Events | Multiple choice | Hard |
| 102 | Build the DOM's listener brain | DOM Events | Coding | Hard |
| 103 | The stub that outlived its test | Testing Lifecycle | Multiple choice | Hard |
| 104 | Nested describes: whose hook goes first? | Testing Lifecycle | Drag & drop | Hard |
| 105 | Build the lifecycle harness itself | Testing Lifecycle | Coding | Hard |
| 106 | A promise pool with a concurrency limit | Async & Promises | Coding | Hard |
| 107 | First success wins — and AggregateError when none does | Async & Promises | Coding | Hard |
| 108 | A queue that keeps submission order | Async & Promises | Coding | Hard |
| 109 | Cancel a timer that has not fired yet | Async & Promises | Coding | Hard |
| 110 | Batch every call made in the same tick | Async & Promises | Coding | Hard |
| 111 | The this machine: an arrow is not a fifth rule | this Binding | Runtime machine | Hard |
| 112 | The this machine: new beats bind | this Binding | Runtime machine | Hard |
| 113 | The frame machine: a rAF inside a rAF | Rendering & Frames | Runtime machine | Hard |
| 114 | The module machine: a circular import, half-built | Modules | Runtime machine | Hard |
| 115 | Six connections, they said | WebSockets | Multiple choice | Hard |
| 116 | The header you cannot send | WebSockets | Multiple choice | Hard |
| 117 | The close code nobody sent | WebSockets | Multiple choice | Hard |
| 118 | send() never says no | WebSockets | Multiple choice | Hard |
| 119 | Connected to nobody | WebSockets | Multiple choice | Hard |
| 120 | Every client came back at the same instant | WebSockets | gap | Hard |