noCommonJs

import { Tabs, TabItem } from '@astrojs/starlight/components';

<Tabs> <TabItem label="JavaScript (and super languages)" icon="seti:javascript"> ## Summary - Rule available since: `v1.9.0` - Diagnostic Category: [`lint/style/noCommonJs`](/reference/diagnostics#diagnostic-category) - This rule isn't recommended, so you need to enable it. - This rule doesn't have a fix. - The default severity of this rule is [**warning**](/reference/diagnostics#warning). - Sources: - Same as [`@typescript-eslint/no-require-imports`](https://typescript-eslint.io/rules/no-require-imports) - Same as [`@typescript-eslint/no-var-requires`](https://typescript-eslint.io/rules/no-var-requires) - Same as [`import/no-commonjs`](https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/no-commonjs.md)

How to configure

json

{
	"linter": {
		"rules": {
			"style": {
				"noCommonJs": "error"
			}
		}
	}
}

Description

Disallow use of CommonJs module system in favor of ESM style imports.

ESM-style imports are modern alternative to CommonJS require imports. Supported by all modern browsers and Node.js versions. Tooling can more easily statically analyze and tree-shake ESM imports compared to CommonJs.

Examples

Invalid

require('node:fs');

<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/no-common-js">lint/style/noCommonJs</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use ESM imports instead of require. > 1 │ require('node:fs'); │ ^^^^^^^^^^^^^^^^^^ 2 │ ℹ ESM-style import statements are more easily statically analyzable and tree-shakable compared to CommonJs require. </code></pre>

module.exports = { a: 'b' }

<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/no-common-js">lint/style/noCommonJs</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use ESM exports instead of module.exports. > 1 │ module.exports = { a: 'b' } │ ^^^^^^^^^^^^^^ 2 │ ℹ ESM-style export statements are more easily statically analyzable and tree-shakable compared to CommonJs module.exports. </code></pre>

exports.a = 'b';

<pre class="language-text"><code class="language-text">code-block.js:1:1 <a href="https://biomejs.dev/linter/rules/no-common-js">lint/style/noCommonJs</a> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ⚠ Use ESM exports instead of module.exports. > 1 │ exports.a = 'b'; │ ^^^^^^^^^ 2 │ ℹ ESM-style export statements are more easily statically analyzable and tree-shakable compared to CommonJs module.exports. </code></pre>

Valid

import fs from 'node:fs';

import('node:fs')

export const a = 'b';

export default { a: 'b' };

Caveats

Rule is automatically disabled inside .cjs and .cts files, because they are explicitly CommonJs files.

This rule could be helpful if you are migrating from CommonJs to ESM, but if you wish to continue using CommonJs, you can safely disable it.

</TabItem> </Tabs>