biome-linting

# Biome Linting

Expert knowledge of Biome's linting capabilities, rule categories, and code quality enforcement for JavaScript and TypeScript projects.

## Overview

Biome's linter provides fast, comprehensive code quality checks with a focus on correctness, performance, security, and best practices. It's designed to catch common bugs and enforce consistent code patterns.

## Core Commands

### Basic Linting

```bash
# Check files without fixing
biome check .

# Check and auto-fix
biome check --write .

# Check specific files
biome check src/**/*.ts

# CI mode (strict, fails on warnings)
biome ci .
```

### Command Options

```bash
# Verbose output
biome check --verbose .

# JSON output
biome check --json .

# Only lint (skip formatting)
biome lint .

# Apply safe fixes only
biome check --write --unsafe=false .
```

## Rule Categories

### Accessibility (a11y)

Rules for web accessibility and WCAG compliance:

```json
{
  "linter": {
    "rules": {
      "a11y": {
        "recommended": true,
        "noAccessKey": "error",
        "noAriaHiddenOnFocusable": "error",
        "noAutofocus": "warn",
        "noBlankTarget": "error",
        "noPositiveTabindex": "error",
        "useAltText": "error",
        "useAnchorContent": "error",
        "useButtonType": "error",
        "useValidAriaProps": "error"
      }
    }
  }
}
```

Common violations:

- Missing alt text on images
- Autofocus on form elements
- Positive tabindex values
- Links without content
- Invalid ARIA properties

### Complexity

Rules to reduce code complexity:

```json
{
  "linter": {
    "rules": {
      "complexity": {
        "recommended": true,
        "noBannedTypes": "error",
        "noExcessiveCognitiveComplexity": "warn",
        "noExtraBooleanCast": "error",
        "noMultipleSpacesInRegularExpressionLiterals": "error",
        "noUselessCatch": "error",
        "noUselessConstructor": "error",
        "noUselessEmptyExport": "error",
        "noUselessFragments": "error",