Convert HTML to Markdown in DOM Javascript.

html2md.js

/*
            (c) Tom Thorogood 2015
          https://tomthorogood.co.uk

Copyright 2015 Tom Thorogood. All rights reserved.
Use of this source code is governed by a
Modified BSD License license that can be found in
the LICENSE file.
*/

window.html2md = function () {
	var ELEMENTS = {
		"#text": function text() {
			// Escape special characters?
			
			for (var pn = this.parentNode; pn; pn = pn.parentNode) {
				if (pn.nodeName === "pre") {
					return this.textContent;
				}
			}
			
			return this.parentNode.nodeName === "ol" || this.parentNode.nodeName === "ul"
				? this.textContent.trim()
				: this.textContent.replace(/\s+/gm, " ");
		},
		"p": function p() {
			return this.attributes.length
				? this.outerHTML
				: this.parentNode.nodeName === "blockquote"
					? "\n> " + convert(this) + "\n"
					: "\n\n" + convert(this) + "\n";
		},
		"a": function a() {
			var href = this.getAttribute("href");
			var title = this.getAttribute("title");
			return this.attributes.length <= 2 && href && (this.attributes.length === 2 ? title : true) && this.children.length === 0
				? "[" + this.textContent + "](" + href + (title ? ' "' + title[1] + '"' : "") + ")"
				: this.outerHTML;
		},
		"h1": hN,
		"h2": hN,
		"h3": hN,
		"h4": hN,
		"h5": hN,
		"h6": hN,
		"br": function br() {
			return this.attributes.length
				? this.outerHTML
				: " \n";
		},
		"hr": function hr() {
			return this.attributes.length
				? this.outerHTML
				: "\n\n---\n";
		},
		"b": strong,
		"strong": strong,
		"i": em,
		"em": em,
		"pre": function pre() {
			return this.attributes.length || this.children.length !== 1 || this.children[0].nodeName != "code"
				? this.outerHTML
				: convert(this);
		},
		"code": function code() {
			return this.attributes.length
				? this.outerHTML
				//: "`" + convert(this) + "`";
				: "    " + convert(this).split("\n").join("\n    ");
		},
		"img": function img() {
			var src = this.getAttribute("src");
			var alt = this.getAttribute("alt");
			var title = this.getAttribute("title");
			return this.attributes.length <= 3 && src && (this.attributes.length === 2 ? title || alt : true) && (this.attributes.length === 3 ? title && alt : true) && this.children.length === 0
				? "![" + alt + "](" + src + (title ? ' "' + title + '"' : "") + ")"
				: this.outerHTML;
		},
		"ol": xl,
		"ul": xl,
		"li": function li() {
			return this.attributes.length
				? this.outerHTML
				: this.parentNode.nodeName === "ol"
					? (Array.prototype.indexOf.call(this.parentNode.children, this) + 1) + ". "
						+ convert(this) + "\n"
					: this.parentNode.nodeName === "ul"
						? "+ " + convert(this) + "\n"
						: this.outerHTML;
		},
		"blockquote": function blockquote() {
			return this.attributes.length
				? this.outerHTML
				: this.children.length !== 0 && Array.prototype.find.call(this.children, function isP(elem) { return elem.nodeName === "p"; })
					? convert(this)
					: "\n> " + convert(this) + "\n";
		},
	};
	
	function hN() {
		return this.attributes.length
			? this.outerHTML
			: "\n\n" + Array((this.nodeName[1]|0) + 1).join("#") + " " + convert(this) + "\n";
	};
	
	function strong() {
		return this.attributes.length
			? this.outerHTML
			: "**" + convert(this) + "**";
	};
	
	function em() {
		return this.attributes.length
			? this.outerHTML
			: "_" + convert(this) + "_";
	};
	
	function xl() {
		return this.attributes.length
			? this.outerHTML
			: "\n" + convert(this) + "\n";
	}
	
	function convert(elem) {
		return Array.prototype.map.call(elem.childNodes, function (child) {
			return child.nodeName in ELEMENTS
				? ELEMENTS[child.nodeName].call(child)
				: child.outerHTML;
		}).join("");
	}
	
	return function html2md(html) {
		var doc = document.implementation.createDocument("http://www.w3.org/1999/xhtml", "html",  null);
		
		var body = document.createElementNS("http://www.w3.org/1999/xhtml", "body");
		doc.documentElement.appendChild(body);
		
		body.innerHTML = html;
		
		return convert(body).replace(/^(?:\r?\n)+|(?:\r?\n)+$/g, "");
	}
}();

html2md(`<h1>HTML Ipsum Presents</h1>

<p><strong>Pellentesque habitant morbi tristique</strong> senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. <em>Aenean ultricies mi vitae est.</em> Mauris placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. Vestibulum erat wisi, condimentum sed, <code>commodo vitae</code>, ornare sit amet, wisi. Aenean fermentum, elit eget tincidunt condimentum, eros ipsum rutrum orci, sagittis tempus lacus enim ac dui. <a href="#">Donec non enim</a> in turpis pulvinar facilisis. Ut felis.</p>

<h2>Header Level 2</h2>

<ol>
   <li>Lorem ipsum dolor sit amet, consectetuer adipiscing elit.</li>
   <li>Aliquam tincidunt mauris eu risus.</li>
</ol>

<blockquote><p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vivamus magna. Cras in mi at felis aliquet congue. Ut a est eget ligula molestie gravida. Curabitur massa. Donec eleifend, libero at sagittis mollis, tellus est malesuada tellus, at luctus turpis elit sit amet quam. Vivamus pretium ornare est.</p></blockquote>

<h3>Header Level 3</h3>

<ul>
   <li>Lorem ipsum dolor sit amet, consectetuer adipiscing elit.</li>
   <li>Aliquam tincidunt mauris eu risus.</li>
</ul>

<pre><code>
#header h1 a { 
	display: block; 
	width: 300px; 
	height: 80px; 
}
</code></pre>`);

license

Copyright (c) 2015, Tom Thorogood.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of the Tom Thorogood nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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