ZeroOne English technical blog

Fix shared objects created by JavaScript Array.fill. Test sparse map callbacks, nested template copies, and matrix rows with independent mutable cells.

Trace why JavaScript regex test() alternates true and false, fix skipped filter results, and verify when resetting lastIndex preserves sticky behavior.

Deduplicate JavaScript objects by ID with tested first-wins and last-wins examples. Verify output order, mixed ID types, missing IDs, and shared references.

Fix nested settings lost during JavaScript object spread. Reproduce overwrite order, preserve defaults, and test undefined, null, arrays, and shared references.

Reproduce JavaScript dates shifting a day in three time zones, then choose date-only storage, local midnight, or explicit UTC without offset hacks.

Fix async filter keeping every item with a tested value-decision pairing, reverse completion trace, and explicit rejection and mutation boundaries.

Fix structuredClone errors from functions, distinguish lost class methods from clone failures, and verify a data-only payload with runnable Node.js checks.

Fix reduce on empty arrays with a tested seed policy: compare omitted and undefined seeds, trace sparse callbacks, and avoid zero for negative maxima.