> ## Documentation Index
> Fetch the complete documentation index at: https://docs.qlty.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# TypeScript Language Support

## Summary

<table className="pretty-table">
  <thead>
    <tr>
      <th style={{ width: "35%" }}>Feature</th>
      <th style={{ width: "20%" }}>Status</th>
      <th style={{ width: "45%" }}>Notes</th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>[Maintainability](/cloud/maintainability/metrics)</td>
      <td>✔</td>
      <td>Complexity, duplication, code smells</td>
    </tr>

    <tr>
      <td>[Linting](/linting)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Auto-formatting](/auto-formatting)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Custom checks](/custom-checks)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Security scanning](/cloud/security/framework)</td>
      <td>✔</td>
      <td>AppSec, dependencies, and secrets</td>
    </tr>

    <tr>
      <td>[Code metrics](/cloud/maintainability/metrics)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Code coverage](/coverage)</td>
      <td>✔</td>

      <td />
    </tr>
  </tbody>
</table>

## Details

<table className="pretty-table">
  <tbody>
    <tr className="divider-row">
      <td style={{ width: "35%" }}>Maintainability</td>

      <td style={{ width: "20%" }} />

      <td style={{ width: "45%" }} />
    </tr>

    <tr>
      <td>[Complexity](/complexity)</td>
      <td>✔</td>
      <td>Aka cognitive complexity</td>
    </tr>

    <tr>
      <td>[Cyclomatic complexity](/complexity#difference-from-cyclomatic-complexity)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Identical code duplication](/duplication)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Similar code duplication](/duplication)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Code smells](/code-smells)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr className="divider-row">
      <td>Linters</td>

      <td />

      <td />
    </tr>

    <tr>
      <td>[ESLint](https://eslint.org/)</td>
      <td>✔</td>
      <td>JavaScript and TypeScript linter</td>
    </tr>

    <tr>
      <td>[OXC](https://oxc-project.github.io/)</td>
      <td>✔</td>
      <td>Fast JavaScript/TypeScript linter</td>
    </tr>

    <tr>
      <td>[Knip](https://github.com/webpro/knip)</td>
      <td>✔</td>
      <td>Find unused files, dependencies and exports</td>
    </tr>

    <tr>
      <td>[Biome](https://biomejs.dev/)</td>
      <td>✔</td>
      <td>Unified toolkit for web projects</td>
    </tr>

    <tr className="divider-row">
      <td>Auto-formatters</td>

      <td />

      <td />
    </tr>

    <tr>
      <td>[Prettier](https://prettier.io/)</td>
      <td>✔</td>
      <td>Opinionated code formatter</td>
    </tr>

    <tr>
      <td>[Biome](https://biomejs.dev/)</td>
      <td>✔</td>
      <td>Includes formatting capabilities</td>
    </tr>

    <tr className="divider-row">
      <td>Custom checks</td>

      <td />

      <td />
    </tr>

    <tr>
      <td>[ast-grep](https://github.com/ast-grep/ast-grep)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Semgrep](https://semgrep.dev)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[ripgrep](https://github.com/BurntSushi/ripgrep)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr className="divider-row">
      <td>Security scanning</td>

      <td />

      <td />
    </tr>

    <tr>
      <td>
        [ESLint with security
        rules](https://github.com/eslint-community/eslint-plugin-security)
      </td>

      <td>✔</td>
      <td>AppSec (SAST)</td>
    </tr>

    <tr>
      <td>[Gitleaks](https://gitleaks.io/)</td>
      <td>✔</td>
      <td>Secrets scanning</td>
    </tr>

    <tr>
      <td>[OSV-Scanner](https://google.github.io/osv-scanner/)</td>
      <td>✔</td>
      <td>Dependency scanning (SCA)</td>
    </tr>

    <tr>
      <td>[Semgrep](https://semgrep.dev)</td>
      <td>✔</td>
      <td>AppSec (SAST)</td>
    </tr>

    <tr>
      <td>[Trivy](https://trivy.dev)</td>
      <td>✔</td>
      <td>Dependency scanning (SCA)</td>
    </tr>

    <tr>
      <td>[TruffleHog](https://trufflesecurity.com/trufflehog)</td>
      <td>✔</td>
      <td>Secrets scanning</td>
    </tr>

    <tr className="divider-row">
      <td>Code coverage</td>

      <td />

      <td />
    </tr>

    <tr>
      <td>[Jest](https://jestjs.io/)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>[Vitest](https://vitest.dev/)</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>LCOV coverage format</td>
      <td>✔</td>

      <td />
    </tr>

    <tr>
      <td>Cobertura coverage format</td>
      <td>✔</td>

      <td />
    </tr>
  </tbody>
</table>

## File extensions

By default, TypeScript files are defined as:

```
[file_types.typescript]
globs = ["*.ts", "*.mts", "*.cts"]
interpreters = ["ts-node", "deno"]

[file_types.tsx]
globs = ["*.tsx", "*.mtsx", "*.ctsx"]
```

These patterns can be overridden from `qlty.toml`.

## Supported TypeScript versions

We officially support TypeScript 3.0 and later for maintainability checks and code coverage. Each plugin may have its own version requirements.