Lykn

ESLint and Biome: When You Need Them

Deno’s built-in tools are the default. ESLint and Biome are alternatives for projects with specific needs.

When to Reach for External Linters

• Project needs framework-specific plugins (React, Vue, Angular)
• Organizational standards require ESLint
• Need custom lint rules Deno doesn’t support
• Want Biome’s speed on very large codebases

ESLint for Lykn Output

Flat config (eslint.config.js):

export default [
  {
    rules: {
      "eqeqeq": ["error", "smart"],
      "no-unused-vars": ["warn", { "argsIgnorePattern": "^_" }],
      "prefer-const": "error",
    }
  }
];

The "smart" option for eqeqeq allows == null while enforcing === everywhere else.

Biome

A single Rust binary that lints and formats in one pass. Install with brew install biome. Fast, minimal config, Prettier-compatible formatting. A solid choice if you need a standalone tool outside Deno’s ecosystem.

The Recommendation

Start with deno lint and deno fmt. They’re already installed, already configured, and already what the lykn project uses. Reach for ESLint or Biome when you have a specific reason to.