In-memory analytics: groupBy with multi-key aggregations, having filters, and pivot helper

Strip/parse ANSI escape sequences: strip, visibleLength, truncateVisible, tokenize with color preservation

Scrub secrets from text and objects: AWS keys, GitHub tokens, JWTs, PEM blocks, bearer headers, hex/base64 keys

Node crypto helpers implemented for real: AES-256-GCM encrypt/decrypt with a portable payload format, scrypt key derivation, timing-safe HMAC-SHA256 sign/verify, and RSA-OAEP encrypt/decrypt with a key-pair generator.

RFC 4180 CSV parser and stringifier with a chunked streaming API, quoted-field/escaped-quote/embedded-newline handling, and opt-in type coercion. Zero runtime dependencies.

Error capture and grouping with rate limiting and breadcrumb tracking

Rule-string validation engine ("required|number|min:18"), nested object schemas, array item validation, custom rules, and full error collection with field paths. Zero runtime dependencies.

Field-level 3-way merge for offline-first sync: auto-merges non-conflicting field changes, resolves true conflicts via lastWrite/preferLocal/preferRemote/custom strategies, and reports every conflict and how it was resolved. Zero runtime dependencies.

Versioned data migrator: register {from, to, migrate} transforms, walk any document to the latest schema version (or a target), support downgrade via revert(), batch helper, and gap/monotonicity validation at registration.

Offline package.json analyzer for loose versions, duplicates, and invalid semver

DB-agnostic migration runner: ordered up/down migrations, pluggable applied-state store (in-memory or JSON file bundled), dry-run mode, and checksum protection against editing already-applied migrations.

URL slugs: unicode to ASCII transliteration, word-boundary truncation, uniqueness helper

In-memory async job queue: named handlers, sliding concurrency limit, per-task retries with exponential backoff + jitter, dead-letter list, priority ordering, graceful drain, and events. Honest about being in-memory; pluggable observer hook for persistenc

Channel-agnostic notification service with templating, retry, and fan-out

Cursor and offset pagination over in-memory arrays, with opaque base64url cursors, tamper detection, and a keyset (seek) helper for pagination that stays stable under concurrent inserts. Zero runtime dependencies.

Event buffer with batched flush, auto-flush on size/interval, and retry-once sink

LRU, LFU, and TTL in-memory cache implementations sharing one interface, each tracking hits/misses/evictions. LRU correctly refreshes recency on get(). Zero runtime dependencies.

A reconnecting WebSocket wrapper with exponential backoff + jitter, heartbeat ping/pong, message queueing while disconnected, and an event emitter API. Bring your own WebSocket implementation.

HTTP cookie parsing and serialization with attribute validation and Set-Cookie parsing

Keep .env and .env.example honest: parse dotenv format, diff two files for drift and leak risk, and generate a safe .env.example. Zero runtime dependencies.