markdown-to-html

Markdown to HTML Conversion

Expert skill for converting Markdown documents to HTML using the marked.js library, or writing data conversion scripts; in this case scripts similar to markedJS/marked repository. For custom scripts knowledge is not confined to marked.js, but data conversion methods are utilized from tools like pandoc and gomarkdown/markdown for data conversion; jekyll/jekyll and gohugoio/hugo for templating systems.

The conversion script or tool should handle single files, batch conversions, and advanced configurations.

When to Use This Skill

• User asks to "convert markdown to html" or "transform md files"
• User wants to "render markdown" as HTML output
• User needs to generate HTML documentation from .md files
• User is building static sites from Markdown content
• User is building template system that converts markdown to html
• User is working on a tool, widget, or custom template for an existing templating system
• User wants to preview Markdown as rendered HTML

Converting Markdown to HTML

Essential Basic Conversions

For more see basic-markdown-to-html.md

    ```markdown
    # Level 1
    ## Level 2

    One sentence with a [link](https://example.com), and a HTML snippet like `<p>paragraph tag</p>`.

    - `ul` list item 1
    - `ul` list item 2

    1. `ol` list item 1
    2. `ol` list item 1

    | Table Item | Description |
    | One | One is the spelling of the number `1`. |
    | Two | Two is the spelling of the number `2`. |

    ```js
    var one = 1;
    var two = 2;

    function simpleMath(x, y) {
     return x + y;
    }
    console.log(simpleMath(one, two));
    ```
    ```

    ```html
    <h1>Level 1</h1>
    <h2>Level 2</h2>

    <p>One sentence with a <a href="https://example.com">link</a>, and a HTML snippet like <code>&lt;p&gt;paragraph tag&lt;/p&gt;</code>.</p>

    <ul>
     <li>`ul` list item 1</li>
     <li>`ul` list item 2</li>
    </ul>

    <ol>
     <li>`ol` list item 1</li>
     <li>`ol` list item 2</li>
    </ol>

    <table>
     <thead>
      <tr>
       <th>Table Item</th>
       <th>Description</th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td>One</td>
       <td>One is the spelling of the number `1`.</td>
      </tr>
      <tr>
       <td>Two</td>
       <td>Two is the spelling of the number `2`.</td>
      </tr>
     </tbody>
    </table>

    <pre>
     <code>var one = 1;
     var two = 2;

     function simpleMath(x, y) {
      return x + y;
     }
     console.log(simpleMath(one, two));</code>
    </pre>
    ```

Code Block Conversions

For more see code-blocks-to-html.md

    ```markdown
    your code here
    ```

    ```html
    <pre><code class="language-md">
    your code here
    </code></pre>
    ```

    ```js
    console.log("Hello world");
    ```

    ```html
    <pre><code class="language-js">
    console.log("Hello world");
    </code></pre>
    ```

    ```markdown
      ```

      ```
      visible backticks
      ```

      ```
    ```

    ```html
      <pre><code>
      ```

      visible backticks

      ```
      </code></pre>
    ```

Collapsed Section Conversions

For more see collapsed-sections-to-html.md

    ```markdown
    <details>
    <summary>More info</summary>

    ### Header inside

    - Lists
    - **Formatting**
    - Code blocks

        ```js
        console.log("Hello");
        ```

    </details>
    ```

    ```html
    <details>
    <summary>More info</summary>

    <h3>Header inside</h3>

    <ul>
     <li>Lists</li>
     <li><strong>Formatting</strong></li>
     <li>Code blocks</li>
    </ul>

    <pre>
     <code class="language-js">console.log("Hello");</code>
    </pre>

    </details>
    ```

Mathematical Expression Conversions

For more see writing-mathematical-expressions-to-html.md

    ```markdown
    This sentence uses `$` delimiters to show math inline: $\sqrt{3x-1}+(1+x)^2$
    ```

    ```html
    <p>This sentence uses <code>$</code> delimiters to show math inline:
     <math-renderer><math xmlns="http://www.w3.org/1998/Math/MathML">
      <msqrt><mn>3</mn><mi>x</mi><mo>−</mo><mn>1</mn></msqrt>
      <mo>+</mo><mo>(</mo><mn>1</mn><mo>+</mo><mi>x</mi>
      <msup><mo>)</mo><mn>2</mn></msup>
     </math>
    </math-renderer>
    </p>
    ```

    ```markdown
    **The Cauchy-Schwarz Inequality**\
    $$\left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)$$
    ```

    ```html
    <p><strong>The Cauchy-Schwarz Inequality</strong><br>
     <math-renderer>
      <math xmlns="http://www.w3.org/1998/Math/MathML">
       <msup>
        <mrow><mo>(</mo>
         <munderover><mo data-mjx-texclass="OP">∑</mo>
          <mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow><mi>n</mi>
         </munderover>
         <msub><mi>a</mi><mi>k</mi></msub>
         <msub><mi>b</mi><mi>k</mi></msub>
         <mo>)</mo>
        </mrow>
        <mn>2</mn>
       </msup>
       <mo>≤</mo>
       <mrow><mo>(</mo>
        <munderover><mo>∑</mo>
         <mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow>
         <mi>n</mi>
        </munderover>
        <msubsup><mi>a</mi><mi>k</mi><mn>2</mn></msubsup>
        <mo>)</mo>
       </mrow>
       <mrow><mo>(</mo>
         <munderover><mo>∑</mo>
          <mrow><mi>k</mi><mo>=</mo><mn>1</mn></mrow>
          <mi>n</mi>
         </munderover>
         <msubsup><mi>b</mi><mi>k</mi><mn>2</mn></msubsup>
         <mo>)</mo>
       </mrow>
      </math>
     </math-renderer></p>
    ```

Table Conversions

For more see tables-to-html.md

    ```markdown
    | First Header  | Second Header |
    | ------------- | ------------- |
    | Content Cell  | Content Cell  |
    | Content Cell  | Content Cell  |
    ```

    ```html
    <table>
     <thead><tr><th>First Header</th><th>Second Header</th></tr></thead>
     <tbody>
      <tr><td>Content Cell</td><td>Content Cell</td></tr>
      <tr><td>Content Cell</td><td>Content Cell</td></tr>
     </tbody>
    </table>
    ```

    ```markdown
    | Left-aligned | Center-aligned | Right-aligned |
    | :---         |     :---:      |          ---: |
    | git status   | git status     | git status    |
    | git diff     | git diff       | git diff      |
    ```

    ```html
    <table>
      <thead>
       <tr>
        <th align="left">Left-aligned</th>
        <th align="center">Center-aligned</th>
        <th align="right">Right-aligned</th>
       </tr>
      </thead>
      <tbody>
       <tr>
        <td align="left">git status</td>
        <td align="center">git status</td>
        <td align="right">git status</td>
       </tr>
       <tr>
        <td align="left">git diff</td>
        <td align="center">git diff</td>
        <td align="right">git diff</td>
       </tr>
      </tbody>
    </table>
    ```

Working with markedJS/marked

Prerequisites

• Node.js installed (for CLI or programmatic usage)
• Install marked globally for CLI: npm install -g marked
• Or install locally: npm install marked

Quick Conversion Methods

See marked.md Quick Conversion Methods

Step-by-Step Workflows

See marked.md Step-by-Step Workflows

CLI Configuration

Using Config Files

Create ~/.marked.json for persistent options:

{
  "gfm": true,
  "breaks": true
}

Or use a custom config:

marked -i input.md -o output.html -c config.json

CLI Options Reference

Option	Description
-i, --input <file>	Input Markdown file
-o, --output <file>	Output HTML file
-s, --string <string>	Parse string instead of file
-c, --config <file>	Use custom config file
--gfm	Enable GitHub Flavored Markdown
--breaks	Convert newlines to <br>
--help	Show all options

Security Warning

⚠️ Marked does NOT sanitize output HTML. For untrusted input, use a sanitizer:

import { marked } from 'marked';
import DOMPurify from 'dompurify';

const unsafeHtml = marked.parse(untrustedMarkdown);
const safeHtml = DOMPurify.sanitize(unsafeHtml);

Recommended sanitizers:

• DOMPurify (recommended)
• sanitize-html
• js-xss

Supported Markdown Flavors

Flavor	Support
Original Markdown	100%
CommonMark 0.31	98%
GitHub Flavored Markdown	97%

Troubleshooting

Issue	Solution
Special characters at file start	Strip zero-width chars: content.replace(/^[\u200B\u200C\u200D\uFEFF]/,"")
Code blocks not highlighting	Add a syntax highlighter like highlight.js
Tables not rendering	Ensure gfm: true option is set
Line breaks ignored	Set breaks: true in options
XSS vulnerability concerns	Use DOMPurify to sanitize output

Working with pandoc

Prerequisites

• Pandoc installed (download from https://pandoc.org/installing.html)
• For PDF output: LaTeX installation (MacTeX on macOS, MiKTeX on Windows, texlive on Linux)
• Terminal/command prompt access

Quick Conversion Methods

Method 1: CLI Basic Conversion

# Convert markdown to HTML
pandoc input.md -o output.html

# Convert with standalone document (includes header/footer)
pandoc input.md -s -o output.html

# Explicit format specification
pandoc input.md -f markdown -t html -s -o output.html

---

*Content truncated.*