New: 98,000+ skills indexed from GitHub repos with 100+ stars · every skill safety-checkedBrowse top skillsTop skills
Esc to closeBrowse all skills
Submit a skillBrowse skills
Submit a skillBrowse skills

Agent skill

Prefer Set Has

by LedgerHQ in LedgerHQ/ledger-live

Prefer Set.has() over Array.includes() for constant allowlists/blocklists.

MITAuto-check passed

Install Prefer Set Has

skills CLI
$ npx skills add LedgerHQ/ledger-live --skill prefer-set-has -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install LedgerHQ/ledger-live prefer-set-has --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/LedgerHQ/ledger-live.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/prefer-set-has .claude/skills/prefer-set-has && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
prefer-set-has
GitHub stars
622
Token cost
~227 tokens
SKILL.md length
73 words
Files
1
Skills in repo
50
Repo updated
First seen
Licence
MIT

At a glance

Prefer Set.has() over Array.includes() for constant allowlists/blocklists.

  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Prefer Set Has is an agent skill from LedgerHQ/ledger-live. Prefer Set.has() over Array.includes() for constant allowlists/blocklists. Read this when reviewing or writing membership checks in TypeScript files.

Its SKILL.md is about 230 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It works with TypeScript. The repository describes itself as: Mono-repository for Ledger Wallet apps and related packages. The licence is MIT.

Example prompts

  • “/prefer-set-has”

What it can do on your machine

Read from SKILL.md and the folder at commit 9c51f17. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are typescript).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Prefer Set Has loads about 227 tokens when it runs. Until then it costs about 41 tokens; SKILL.md has 73 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~41
When it runs · the whole SKILL.md, loaded when a task matches
~227

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from LedgerHQ/ledger-live at commit 9c51f17, republished under its MIT licence (© LedgerHQ). 73 words, ~227 tokens.

Download SKILL.mdSave it as .claude/skills/prefer-set-has/SKILL.md (or your agent's skills folder).
name
prefer-set-has
description
Prefer Set.has() over Array.includes() for constant allowlists/blocklists. Read this when reviewing or writing membership checks in TypeScript files.

Prefer Set.has() over Array.includes()

When checking membership in a constant list of known values (allowlists, blocklists, enum-like sets), use a Set with .has() instead of an array with .includes().

typescript
// ❌ BAD
const ALLOWED = ["a", "b", "c"];
if (ALLOWED.includes(value)) { … }

// ✅ GOOD
const ALLOWED = new Set(["a", "b", "c"]);
if (ALLOWED.has(value)) { … }

Why: Set.has() is O(1) vs .includes() O(n), communicates "membership test" intent more clearly, and avoids accidental mutation of the backing array.

When .includes() is fine: Searching within a dynamic or short-lived array (e.g. function parameters, user input) where creating a Set would add noise.

© LedgerHQ, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/prefer-set-has of LedgerHQ/ledger-live.

Open the folder on GitHubat commit 9c51f17

Compare with similar skills

Prefer Set Has next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Prefer Set Has compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Prefer Set Has this skillLedgerHQ/ledger-live622—~227Automated safety check: PassMIT
MCP Server Builderanthropics/skills180k63 repos~2.3kAutomated safety check: PassApache-2.0
Web Artifacts Builderanthropics/skills180k41 repos~769Automated safety check: PassApache-2.0
Typescript Advanced Typesrolling-scopes/rsschool-app10k25 repos~4.2kAutomated safety check: PassMPL-2.0
Code Review ChecklistshareAI-lab/learn-claude-code78k5 repos~1.1kAutomated safety check: PassMIT
MCP Server BuildershareAI-lab/learn-claude-code78k5 repos~1.2kAutomated safety check: PassMIT

Similar skills

  • MCP Server Builder

    anthropics/skills

    Official

    Guides the design and implementation of Model Context Protocol servers in TypeScript or Python, from tool naming and error messages to evaluation.

    180k GitHub starsUsed in 63 repos~2.3k tokens
    Agent WorkflowsAuto-check passed

  • Web Artifacts Builder

    anthropics/skills

    Official

    Builds multi-component claude.ai HTML artifacts as a small React, TypeScript and Tailwind project, then bundles it into one shareable HTML file.

    180k GitHub starsUsed in 41 repos~769 tokens
    Frontend & DesignAuto-check passed

  • Typescript Advanced Types

    rolling-scopes/rsschool-app

    Master TypeScript's advanced type system including generics, conditional types, mapped types, template literals, and utility types for building type-safe applications.

    10k GitHub starsUsed in 25 repos~4.2k tokens
    DevelopmentAuto-check passed

  • Code Review Checklist

    shareAI-lab/learn-claude-code

    Reviews code against a five-part checklist covering security, correctness, performance, maintainability and testing, and reports findings in a fixed format.

    78k GitHub starsUsed in 5 repos~1.1k tokens
    DevelopmentAuto-check passed

  • MCP Server Builder

    shareAI-lab/learn-claude-code

    Walks through building MCP servers in Python or TypeScript that expose tools, resources and prompts to Claude, with templates, registration and testing.

    78k GitHub starsUsed in 5 repos~1.2k tokens
    Agent WorkflowsAuto-check passed

  • Nx Import

    nrwl/nx

    Import, merge, or combine repositories into an Nx workspace using nx import.

    29k GitHub starsUsed in 6 repos~3.5k tokens
    DevelopmentAuto-check passed

More from LedgerHQ/ledger-live

All 50 skills in this repo

  • Impacting PRs

    LedgerHQ/ledger-live

    Find which open PRs are impacted by a migration/sunset/refactor and notify their authors — blocking review when the old path is already gone from develop, heads-up comment when it is only deprecated…

    622 GitHub stars~3.3k tokensUpdated today
    Auto-check passed

  • Cloud Sync Module

    LedgerHQ/ledger-live

    Write, review or debug a cloudSyncModule.ts — a CloudSyncDataManager that syncs one slice of user data through Ledger Sync (Cloud Sync).

    622 GitHub stars~2.4k tokensUpdated today
    Auto-check passed

  • Codeownership

    LedgerHQ/ledger-live

    Maintain CODEOWNERS file and team directories. An agent skill from LedgerHQ/ledger-live.

    622 GitHub stars~687 tokensUpdated today
    Auto-check passed

  • Coin Families Contract

    LedgerHQ/ledger-live

    Coin-specific families logic must live in families/. An agent skill from LedgerHQ/ledger-live.

    622 GitHub stars~1k tokensUpdated today
    Auto-check passed

  • Data Layer Advanced

    LedgerHQ/ledger-live

    Structure a Ledger Wallet data layer where one API response serves several entities.

    622 GitHub stars~509 tokensUpdated today
    Auto-check passed

  • Debug Rn Native Crash

    LedgerHQ/ledger-live

    Investigate native React Native crashes (Fabric/Hermes/iOS) in ledger-live-mobile when JS error logs are missing or unhelpful.

    622 GitHub stars~1.2k tokensUpdated today
    Auto-check passed

Works with

Questions about Prefer Set Has

What does Prefer Set Has do?

Prefer Set.has() over Array.includes() for constant allowlists/blocklists. Prefer Set Has is an agent skill from LedgerHQ/ledger-live.includes() for constant allowlists/blocklists.

How do I install Prefer Set Has in Claude Code?

Run `npx skills add LedgerHQ/ledger-live --skill prefer-set-has -a claude-code`. Or copy the skill folder (.agents/skills/prefer-set-has in LedgerHQ/ledger-live) into .claude/skills/prefer-set-has in your project. Claude Code loads it when a task matches its description.

How do I install Prefer Set Has in Codex?

Run `npx skills add LedgerHQ/ledger-live --skill prefer-set-has -a codex`. Or copy the skill folder (.agents/skills/prefer-set-has in LedgerHQ/ledger-live) into .agents/skills/prefer-set-has in your project. Codex loads it when a task matches its description.

Can I use Prefer Set Has in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add LedgerHQ/ledger-live --skill prefer-set-has -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/prefer-set-has, .gemini/skills/prefer-set-has, .github/skills/prefer-set-has and .opencode/skills/prefer-set-has in your project.

What does Prefer Set Has need to run?

SKILL.md names no scripts, command-line tools or credentials: Prefer Set Has is instructions for the agent only.

Does Prefer Set Has access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Prefer Set Has safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Prefer Set Has use?

Prefer Set Has is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Prefer Set Has use?

About 227 tokens (SKILL.md is roughly 908 characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Prefer Set Has?

Skills that share tags, products or a category with Prefer Set Has: MCP Server Builder (anthropics/skills, 180k stars), Web Artifacts Builder (anthropics/skills, 180k stars), Typescript Advanced Types (rolling-scopes/rsschool-app, 10k stars) and Code Review Checklist (shareAI-lab/learn-claude-code, 78k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Prefer Set Has?

LedgerHQ (a GitHub organization) maintains it in LedgerHQ/ledger-live, which has 622 GitHub stars. The repository holds 50 skills in this directory. The repository was last updated on October 9, 2026.

Source: LedgerHQ/ledger-live on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.