JavaScript Language Support - Qlty Docs

Summary

Feature	Status	Notes
Maintainability	✔	Complexity, duplication, code smells
Linting	✔
Auto-formatting	✔
Custom checks	✔
Security scanning	✔	AppSec, dependencies, and secrets
Code metrics	✔
Code coverage	✔

Details

Maintainability
Complexity	✔	Aka cognitive complexity
Cyclomatic complexity	✔
Identical code duplication	✔
Similar code duplication	✔
Code smells	✔
Linters
ESLint	✔	Pluggable linter for JavaScript
OXC	✔	Fast JavaScript linter
Knip	✔	Find unused files, dependencies and exports
Biome	✔	Unified toolkit for web projects
Auto-formatters
Prettier	✔	Opinionated code formatter
Biome	✔	Includes formatting capabilities
Custom checks
ast-grep	✔
Semgrep	✔
ripgrep	✔
Security scanning
ESLint with security rules	✔	AppSec (SAST)
Gitleaks	✔	Secrets scanning
OSV-Scanner	✔	Dependency scanning (SCA)
Semgrep	✔	AppSec (SAST)
Trivy	✔	Dependency scanning (SCA)
TruffleHog	✔	Secrets scanning
Code coverage
Jest	✔
Vitest	✔
Mocha	✔
LCOV coverage format	✔
Cobertura coverage format	✔

File extensions

By default, JavaScript files are defined as:

[file_types.javascript]
globs = ["*.js", "*.mjs", "*.cjs", "**/Jakefile"]
interpreters = [
  "rhino",
  "gjs",
  "qjs",
  "js",
  "chakra",
  "v8-shell",
  "v8",
  "node",
  "d8",
]

[file_types.jsx]
globs = ["*.jsx", "*.mjsx", "*.cjsx"]

These patterns can be overridden from qlty.toml.

Supported JavaScript versions

We support modern JavaScript (ES2015+) for maintainability checks and code coverage. Each plugin may have its own version requirements.

See also

TypeScript