Convert HTML to Markdown

Writes each node as CommonMark text, for reading, for notes, or as input to a language model. Text is skipped and collapsed as html_text_clean() does, and Markdown-significant characters in it are escaped, so the text reads back as written.

Usage

html_markdown(x)

Arguments

x

A zuhtml_document or zuhtml_nodeset.

Value

A character vector as long as x: the Markdown of each element, document, fragment or text node, without a trailing newline; NA for other nodes and for missing nodes.

Details

The conversion covers:

• headings (# to ######), paragraphs and the other block elements (separated by blank lines), and thematic breaks (<hr>, as ---);

• emphasis (<em>, <i>) as *...* and strong (<strong>, <b>) as **...**, and inline code (<code>, <kbd>, <samp>, <tt>) as a code span;

• <pre> as a fenced code block, with its language when a language-* or lang-* class names one;

• block quotes, and ordered and unordered lists, nested, with start, reversed and value honored; empty list items are left out;

• links and images, their URLs resolved against the document's base URL as html_url() does, or as written where that is not possible; <a> without href is plain text, and <img> without src is left out;

• <br> as a hard line break;

• data tables as GFM pipe tables: tables in which no cell spans rows or columns and every cell holds only inline content (no paragraphs, lists, headings, <div>s, code blocks or tables). The first row is the header row, and cell contents stay on one line. Other tables, such as tables used for page layout, are written as their content, one paragraph per row, with cells separated by spaces.

<head>, <script>, <style>, <template>, <iframe>, <svg> and comments are left out. Other elements contribute their text only. Markup that crosses block boundaries, such as <b> around two paragraphs, is closed and reopened in each block.

See also

html_text_clean() for plain text.

Other node values: html_attr(), html_name(), html_serialize(), html_strings(), html_text(), html_text_clean()

Examples

doc <- html_parse(paste0(
  "<h1>Release notes</h1>",
  "<p>Version <b>2.0</b> adds <code>fetch()</code>. ",
  "See <a href='changes.html'>the changes</a>.</p>",
  "<ul><li>Faster parsing</li><li>New <i>options</i>:",
  "<ol><li>limits</li><li>encoding</li></ol></li></ul>",
  "<table><tr><th>Item</th><th>Cost</th></tr>",
  "<tr><td>Tea</td><td>3</td></tr></table>"
), base_url = "https://example.org/docs/")
cat(html_markdown(doc))
#> # Release notes
#> 
#> Version **2.0** adds `fetch()`. See [the changes](https://example.org/docs/changes.html).
#> 
#> - Faster parsing
#> - New *options*:
#>   1. limits
#>   2. encoding
#> 
#> | Item | Cost |
#> | --- | --- |
#> | Tea | 3 |