AgentSkillsCN

npm-exists

检查 npm 包名是否已在注册表中存在。当用户询问某个包名是否可用、想要检查包的存在性，或核实某个包是否已发布时，可使用此功能。

SKILL.md
--- frontmatter
name: npm-exists
description: Check if an npm package name exists in the registry. Use when the user asks if a package name is available, wants to check package existence, or verify if a package is published.

Check npm Package Existence

Check if a package name exists in the npm registry.

Usage

bash
npx tsx scripts/exists.ts <package-name> [options]

Arguments

ArgumentRequiredDescription
package-nameYesThe exact package name to check (case-sensitive)

Options

OptionDescription
--no-cacheBypass cache and fetch fresh data from API

Output

Package exists:

code
✓ Package "react" exists
  URL: https://www.npmjs.com/package/react
  Published: Yes

Package does not exist:

code
✗ Package "my-awesome-pkg-12345" does not exist
  The name is available for use

Script Execution (Preferred)

bash
npx tsx scripts/exists.ts <package-name> [options]

Options:

  • •--no-cache - Bypass cache and fetch fresh data from API

Run from the npm-registry plugin directory: ~/.claude/plugins/cache/npm-registry/

Existence Check API

code
HEAD https://registry.npmjs.org/{package}

Parameters

ParameterRequiredDescription
packageYesThe exact package name to check (case-sensitive)

Examples

Check if a package exists:

code
HEAD https://registry.npmjs.org/react

For scoped packages:

code
HEAD https://registry.npmjs.org/@babel/core

Response Interpretation

Package exists - HTTP 200 OK

  • •The package is published and available
  • •You can use npm info or npm install with this name

Package does not exist - HTTP 404 Not Found

  • •The package name is available for use
  • •No package with this exact name exists in the registry

Before publishing a new package, verify the name is available:

bash
npx tsx exists.ts my-new-package

Validate Package Name

Confirm a package exists before installing or using it:

bash
npx tsx exists.ts some-dependency

Scoped Packages

Check scoped package names:

bash
npx tsx exists.ts @myorg/package-name

Naming Rules

Package names must:

  • •Start with a letter, number, @, or _
  • •Contain only URL-safe characters (letters, numbers, hyphens, underscores)
  • •Not start with . or _
  • •Not contain spaces
  • •Not exceed 214 characters
  • •Not be the same as a node.js/core module name

Scoped packages (@scope/name) have additional rules:

  • •Scope must be the username of the npm owner
  • •Scope must be followed by a slash

Caching

Existence checks are cached for 1 hour. Package availability changes infrequently, so short cache times provide a good balance between freshness and performance.

Use the --no-cache flag to bypass the cache.

Related

  • •Use npm-info to get detailed package metadata when it exists
  • •Use npm-search to find similar or alternative packages
  • •Use npm-downloads to see package statistics

Error Handling

Network errors: The npm registry may be temporarily unavailable. Retry after a brief delay.

Rate limiting: While existence checks use HEAD requests (minimal bandwidth), excessive rapid requests may be rate-limited.

Scoped packages: Remember that scoped packages require the full name including the scope (e.g., @babel/core, not just core).