Programming Languages

JavaScript Language Support

Summary

FeatureStatusNotes
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