HAST Utility: Is Conditional Comment

Common errors

• ERR_REQUIRE_ESM

  cause Attempting to use `require()` to import `hast-util-is-conditional-comment` in a CommonJS module.
  fix Change your import statement to `import { isConditionalComment } from 'hast-util-is-conditional-comment';` and ensure your environment supports ESM.

• TypeError: isConditionalComment is not a function

  cause Incorrectly importing `isConditionalComment` as a default import, or attempting to destructure from a module that has no named export.
  fix The package has no default export. Always use named import syntax: `import { isConditionalComment } from 'hast-util-is-conditional-comment';`.

Warnings

• breaking Version 3.x of `hast-util-is-conditional-comment` is ESM-only and requires Node.js 16 or later. Attempting to use it in a CommonJS environment or older Node.js versions will result in import errors or runtime failures.
  Fix: Ensure your project is configured for ESM (e.g., `"type": "module"` in `package.json` or `.mjs` files) and upgrade Node.js to version 16 or newer. Replace `require()` calls with `import` statements.
• gotcha While this utility itself only checks node types and does not modify the AST, working with `hast` trees in general (especially with other `rehype` plugins) can expose applications to Cross-Site Scripting (XSS) vulnerabilities if not handled carefully.
  Fix: Always use `rehype-sanitize` when processing untrusted HTML to prevent potential XSS attacks, especially if other plugins are transforming the tree.
• gotcha This package specifically identifies legacy Internet Explorer conditional comments. It will not identify other types of special comments or directives, only the specific patterns recognized as IE conditional comments.
  Fix: If you need to identify other specific comment patterns, you will need to implement custom logic or use other `hast` utilities designed for broader comment analysis.

Install

• npm install hast-util-is-conditional-comment npm
• yarn add hast-util-is-conditional-comment yarn
• pnpm add hast-util-is-conditional-comment pnpm

Imports

• isConditionalComment
  wrong:

  const isConditionalComment = require('hast-util-is-conditional-comment')

  correct:

  import { isConditionalComment } from 'hast-util-is-conditional-comment'

  This package is ESM-only since v3 and exports `isConditionalComment` as a named export. CommonJS `require` is not supported.
• Node
  wrong:

  import { Node } from 'hast'

  correct:

  import type { Node } from 'hast'

  For TypeScript users, import `Node` as a type from `hast` to ensure correct type checking for AST nodes.
• u
  wrong:

  import u from 'unist-builder'

  correct:

  import { u } from 'unist-builder'

  `u` from `unist-builder` is often used for creating `unist` (and by extension `hast`) nodes in examples. It is a named export, not a default export.

Quickstart

Demonstrates how to import and use `isConditionalComment` to programmatically check various `hast` comment nodes for Internet Explorer conditional comment syntax.

import { isConditionalComment } from 'hast-util-is-conditional-comment';
import { u } from 'unist-builder'; // u for creating unist/hast nodes

// A valid IE conditional comment
const ieConditionalComment = u({ type: 'comment', value: '[if IE]>...<![endif]' });
// An IE conditional end comment
const ieConditionalEndComment = u({ type: 'comment', value: '<![endif]' });
// A regular HTML comment
const regularComment = u({ type: 'comment', value: 'This is a regular comment' });

console.log('Is IE Conditional Comment (full):', isConditionalComment(ieConditionalComment));
// => true
console.log('Is IE Conditional Comment (end):', isConditionalComment(ieConditionalEndComment));
// => true
console.log('Is Regular Comment:', isConditionalComment(regularComment));
// => false