# Es Toolkit > Up-to-date es-toolkit documentation reference. Use when writing JavaScript/TypeScript code – writing new utility helpers, working with arrays/objects/Maps/Sets/Promises/math/string manipulation, refactoring code, reviewing code, evaluating whether a custom utility can be replaced with es-toolkit, or when explicitly asked to scan/refactor code toward es-toolkit functions (for example, "Go through the codebase and find potential cases where es-toolkit could be used instead of custom implementations") Use when this capability is needed. - Skill: `tomevault-io/es-toolkit` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/es-toolkit` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/es-toolkit/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/es-toolkit --- # es-toolkit Run initialization first to sync references for the target project's installed `es-toolkit` version. If `package.json` is missing, does not include `es-toolkit`, or contains an unparsable `es-toolkit` range, initialization falls back to the latest `es-toolkit` release: ```sh sh ./scripts/init.sh [/path/to/project/package.json] ``` Treat initialization as a hard prerequisite: - Do not read any file under `references/` until `init.sh` exits with code `0`. - Do not run initialization and reference reads in parallel. - If initialization fails, stop and report the error instead of reading references. When writing/refactoring/reviewing utility code, check the references first and prefer an existing `es-toolkit` function over custom implementations whenever behavior matches. Do not use functions under `compat` ("Lodash compatibility"). ## References (available once initialization is complete) - [Array Utilities](references/array-utilities.md) - [Function Utilities](references/function-utilities.md) - [Map Utilities](references/map-utilities.md) - [Math Utilities](references/math-utilities.md) - [Object Utilities](references/object-utilities.md) - [Predicates](references/predicates.md) - [Promise Utilities](references/promise-utilities.md) - [String Utilities](references/string-utilities.md) - [Set Utilities](references/set-utilities.md) - [Utility Functions](references/utility-functions.md) - [Errors](references/errors.md) --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/deepfriedmind) — claim your Tome and manage your conversions.