micromark Character Classifier Utility

2.0.1 · active · verified Sun Apr 19

The `micromark-util-classify-character` package, currently at version 2.0.1, is a focused utility within the `micromark` ecosystem designed to classify individual Unicode character codes. It categorizes characters into three groups: whitespace, punctuation, or neither. This classification is primarily used in `micromark` extensions, particularly for determining the opening and closing behavior of 'attention' sequences such as emphasis and strong formatting, which depend on the character classes surrounding the sequence. As a part of the actively maintained `micromark` project, its release cadence is tied to the broader library. A key differentiator is its low-level, performance-optimized approach to character classification, directly supporting `micromark`'s parsing algorithms. The package is ESM-only, requiring Node.js version 16 or newer, and ships with complete TypeScript type definitions, making it suitable for modern JavaScript and TypeScript environments.

Common errors

```
ReferenceError: require is not defined
```
cause Attempting to use CommonJS `require` to import an ESM-only package in an ES module context (e.g., in a `.mjs` file or when `"type": "module"` is set in `package.json`).

fix Change `const { classifyCharacter } = require('micromark-util-classify-character');` to `import { classifyCharacter } from 'micromark-util-classify-character';`
```
ERR_REQUIRE_ESM
```
cause Attempting to use CommonJS `require` to import `micromark-util-classify-character`, which is an ES module, in a CommonJS context.

fix Either convert your consuming module to ESM by adding `"type": "module"` to your `package.json` or changing its extension to `.mjs`, then use `import` syntax. Alternatively, if your project must remain CommonJS, you might need to use a dynamic import: `import('micromark-util-classify-character').then(mod => mod.classifyCharacter(...))`.

Warnings

breaking This package is ESM-only. Attempting to import it using CommonJS `require()` will result in an error.
Fix: Migrate your project to use ES modules (`import` statements) or ensure your environment is configured for ESM.
breaking `micromark-util-classify-character@2` requires Node.js version 16 or higher.
Fix: Upgrade your Node.js runtime to version 16.x or newer.
gotcha This utility is part of the `micromark` ecosystem and is specifically designed to work with `micromark@3`. While it might function with other versions, compatibility is only guaranteed for `micromark@3`.
Fix: Ensure your `micromark` package is installed at version `3.x`.

Install

npm install micromark-util-classify-character npm
yarn add micromark-util-classify-character yarn
pnpm add micromark-util-classify-character pnpm

Imports

classifyCharacter

wrong:

const { classifyCharacter } = require('micromark-util-classify-character');

correct:

import { classifyCharacter } from 'micromark-util-classify-character';

This package is ESM only. CommonJS `require` statements are not supported for this module since version 1.0.0.

characterGroupWhitespace
wrong:
```
const { characterGroupWhitespace } = require('micromark-util-constants');
```
correct:
```
import { characterGroupWhitespace } from 'micromark-util-constants';
```
Constants like `characterGroupWhitespace` and `characterGroupPunctuation` are used with `classifyCharacter` and typically imported from `micromark-util-constants`. This package is also ESM-only.
Code
```
import type { Code } from 'micromark-util-types';
```
While `micromark-util-classify-character` ships its own types, if you need the `Code` type for parameters, it's typically imported from `micromark-util-types` within the micromark ecosystem.

Quickstart

This quickstart demonstrates how to import and use the `classifyCharacter` function to determine if a character code represents whitespace, punctuation, or neither. It also shows how to use the constants for comparison.

import { classifyCharacter } from 'micromark-util-classify-character';
import { characterGroupWhitespace, characterGroupPunctuation } from 'micromark-util-constants';

/**
 * Classify a given character and return its category as a string.
 * @param {string | null} char The character to classify, or null for EOF.
 * @returns {string} The classification result.
 */
function getCharacterCategory(char: string | null): string {
  const code = char === null ? null : char.charCodeAt(0);
  const classification = classifyCharacter(code);

  switch (classification) {
    case characterGroupWhitespace:
      return `'${char}' (code: ${code}) is classified as WHITESPACE.`;
    case characterGroupPunctuation:
      return `'${char}' (code: ${code}) is classified as PUNCTUATION.`;
    default:
      return `'${char}' (code: ${code}) is classified as NEITHER.`;
  }
}

console.log(getCharacterCategory(' ')); // Space character
console.log(getCharacterCategory('\t')); // Tab character
console.log(getCharacterCategory('.')); // Period character
console.log(getCharacterCategory('!')); // Exclamation mark
console.log(getCharacterCategory('a')); // Letter 'a'
console.log(getCharacterCategory('7')); // Digit '7'
console.log(getCharacterCategory(null)); // End of file (EOF) is treated as whitespace

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