| # | title | topic | type | difficulty |
|---|---|---|---|---|
| 1 | Group transactions by risk bucket | Objects | Coding | Hard |
| 2 | Rebuild Object.groupBy — null prototype included | Objects | Coding | Hard |
| 3 | deepEqual that survives circular references | Objects | Coding | Hard |
| 4 | Group transactions — approach 2: reduce(), no Object.groupBy | Objects | Coding | Hard |