html2markdown.js

/**
 * html2markdown - An HTML to Markdown converter.
 *
 * This implementation uses HTML or DOM parsing for conversion. Parsing code was
 * abstracted out in a parsing function which should be easy to remove in favor
 * of other parsing libraries.
 *
 * Converted MarkDown was tested with ShowDown library for HTML rendering. And
 * it tries to create MarkDown that does not confuse ShowDown when certain
 * combination of HTML tags come together.
 *
 * @author Himanshu Gilani
 * @author Kates Gasis (original author)
 *
 */

/**
 * html2markdown
 * @param html - html string to convert
 * @return converted markdown text
 */

/*
 Universal JavaScript Module, supports AMD (RequireJS), Node.js, and the browser.
 https://gist.github.com/kirel/1268753
*/

(function (name, definition) {
	if (typeof define === 'function') { // AMD
		define(definition);
	} else if (typeof module !== 'undefined' && module.exports) { // Node.js
		module.exports = definition();
	} else { // Browser
		var theModule = definition(), global = this, old = global[name];
		theModule.noConflict = function () {
			global[name] = old;
			return theModule;
		};
		global[name] = theModule;
	}
})('html2markdown', function() {

function trim(value) {
	return value.replace(/^\s+|\s+$/g,"");
}

function endsWith(value, suffix) {
	return value.match(suffix+"$") == suffix;
}

function startsWith(value, str) {
	return value.indexOf(str) == 0;
}

function html2markdown(html, opts) {
	opts = opts || {};

	var nodeList = [];
	var listTagStack = [];
	var linkAttrStack = [];
	var blockquoteStack = [];
	var preStack = [];
	var codeStack = [];
	var links = [];
	var inlineStyle = opts['inlineStyle'] || false;
	var parser = opts['parser'];
	var markdownTags = {
		"hr": "- - -\n\n",
		"br": "  \n",
		"title": "# ",
		"h1": "# ",
		"h2": "## ",
		"h3": "### ",
		"h4": "#### ",
		"h5": "##### ",
		"h6": "###### ",
		"b": "**",
		"strong": "**",
		"i": "_",
		"em": "_",
		"dfn": "_",
		"var": "_",
		"cite": "_",
		"span": " ",
		"ul": "* ",
		"ol": "1. ",
		"dl": "- ",
		"blockquote": "> "
	};

	if (!parser && typeof markdownDOMParser !== 'undefined') {
		parser = markdownDOMParser;
	}

	function getListMarkdownTag() {
		var listItem = "";
		if (listTagStack) {
			for (var i = 0; i < listTagStack.length - 1; i++) {
				listItem += "  ";
			}
		}
		listItem += peek(listTagStack);
		return listItem;
	}

	function convertAttrs(attrs) {
		var attributes = {};
		for (var k in attrs) {
			var attr = attrs[k];
			attributes[attr.name] = attr;
		}
		return attributes;
	}

	function peek(list) {
		if (list && list.length > 0) {
			return list.slice(-1)[0];
		}
		return "";
	}

	function peekTillNotEmpty(list) {
		if (!list) {
			return "";
		}

		for (var i = list.length - 1; i >= 0; i--){
			if (list[i] != "") {
				return list[i];
			}
		}
		return "";
	}

	function removeIfEmptyTag(start) {
		var cleaned = false;
		if (start == peekTillNotEmpty(nodeList)) {
			while (peek(nodeList) != start) {
				nodeList.pop();
			}
			nodeList.pop();
			cleaned = true;
		}
		return cleaned;
	}

	function sliceText(start) {
		var text = [];
		while (nodeList.length > 0 && peek(nodeList) != start) {
			var t = nodeList.pop();
			text.unshift(t);
		}
		return text.join("");
	}

	function block(isEndBlock) {
		var lastItem = nodeList.pop();
		if (!lastItem) {
			return;
		}

		if (!isEndBlock) {
			var block;
			if (/\s*\n\n\s*$/.test(lastItem)) {
				lastItem = lastItem.replace(/\s*\n\n\s*$/, "\n\n");
				block = "";
			} else if (/\s*\n\s*$/.test(lastItem)) {
				lastItem = lastItem.replace(/\s*\n\s*$/, "\n");
				block = "\n";
			} else if (/\s+$/.test(lastItem)) {
				block = "\n\n";
			} else {
				block = "\n\n";
			}

			nodeList.push(lastItem);
			nodeList.push(block);
		} else {
			nodeList.push(lastItem);
			if (!endsWith(lastItem, "\n")) {
				nodeList.push("\n\n");
			}
		}
	}

	function listBlock() {
		if (nodeList.length > 0) {
			var li = peek(nodeList);

			if (!endsWith(li, "\n")) {
				nodeList.push("\n");
			}
		} else {
			nodeList.push("\n");
		}
	}

	parser(html, {
		start: function(tag, attrs, unary) {
			tag = tag.toLowerCase();

			if (unary && (tag != "br" && tag != "hr" && tag != "img")) {
				return;
			}

			switch (tag) {
			case "br":
				nodeList.push(markdownTags[tag]);
				break;
			case "hr":
				block();
				nodeList.push(markdownTags[tag]);
				break;
			case "title":
			case "h1":
			case "h2":
			case "h3":
			case "h4":
			case "h5":
			case "h6":
				block();
				nodeList.push(markdownTags[tag]);
				break;
			case "b":
			case "strong":
			case "i":
			case "em":
			case "dfn":
			case "var":
			case "cite":
				nodeList.push(markdownTags[tag]);
				break;
			case "code":
			case "span":
				if (preStack.length > 0) {
					break;
				} else if (!/\s+$/.test(peek(nodeList))) {
					nodeList.push(markdownTags[tag]);
				}
				break;
			case "p":
			case "div":
			case "table":
			case "tbody":
			case "tr":
			case "td":
				block();
				break;
			case "ul":
			case "ol":
			case "dl":
				listTagStack.push(markdownTags[tag]);
				// lists are block elements
				if (listTagStack.length > 1) {
					listBlock();
				} else {
					block();
				}
				break;
			case "li":
			case "dt":
				var li = getListMarkdownTag();
				nodeList.push(li);
				break;
			case "a":
				var attribs = convertAttrs(attrs);
				linkAttrStack.push(attribs);
				nodeList.push("[");
				break;
			case "img":
				var attribs = convertAttrs(attrs);
				var alt, title, url;

				attribs["src"] ? url = attribs["src"].value : url = "";
				if (!url) {
					break;
				}

				attribs['alt'] ? alt = trim(attribs['alt'].value) : alt = "";
				attribs['title'] ? title = trim(attribs['title'].value) : title = "";

				// if parent of image tag is nested in anchor tag use inline style
				if (!inlineStyle && !startsWith(peekTillNotEmpty(nodeList), "[")) {
					var l = links.indexOf(url);
					if (l == -1) {
						links.push(url);
						l=links.length-1;
					}

					block();
					nodeList.push("![");
					if (alt!= "") {
						nodeList.push(alt);
					} else if (title != null) {
						nodeList.push(title);
					}

					nodeList.push("][" + l + "]");
					block();
				} else {
					//if image is not a link image then treat images as block elements
					if (!startsWith(peekTillNotEmpty(nodeList), "[")) {
						block();
					}

					nodeList.push("![" + alt + "](" + url + (title ? " \"" + title + "\"" : "") + ")");

					if (!startsWith(peekTillNotEmpty(nodeList), "[")) {
						block(true);
					}
				}
				break;
			case "blockquote":
				//listBlock();
				block();
				blockquoteStack.push(markdownTags[tag]);
				break;
			case "pre":
				block();
				preStack.push(true);
				nodeList.push("    ");
				break;
			case "table":
				nodeList.push("<table>");
				break;
			case "thead":
				nodeList.push("<thead>");
				break;
			case "tbody":
				nodeList.push("<tbody>");
				break;
			case "tr":
				nodeList.push("<tr>");
				break;
			case "td":
				nodeList.push("<td>");
				break;
			}
		},
		chars: function(text) {
			if (preStack.length > 0) {
				text = text.replace(/\n/g,"\n    ");
			} else if (trim(text) != "") {
				text = text.replace(/\s+/g, " ");

				var prevText = peekTillNotEmpty(nodeList);
				if (/\s+$/.test(prevText)) {
					text = text.replace(/^\s+/g, "");
				}
			} else {
				nodeList.push("");
				return;
			}

			//if(blockquoteStack.length > 0 && peekTillNotEmpty(nodeList).endsWith("\n")) {
			if (blockquoteStack.length > 0) {
				nodeList.push(blockquoteStack.join(""));
			}

			nodeList.push(text);
		},
		end: function(tag) {
			tag = tag.toLowerCase();

		switch (tag) {
			case "title":
			case "h1":
			case "h2":
			case "h3":
			case "h4":
			case "h5":
			case "h6":
				if(!removeIfEmptyTag(markdownTags[tag])) {
					block(true);
				}
				break;
			case "p":
			case "div":
			case "table":
			case "tbody":
			case "tr":
			case "td":
				while(nodeList.length > 0 && trim(peek(nodeList)) == "") {
					nodeList.pop();
				}
				block(true);
				break;
			case "b":
			case "strong":
			case "i":
			case "em":
			case "dfn":
			case "var":
			case "cite":
				if (!removeIfEmptyTag(markdownTags[tag])) {
					nodeList.push(trim(sliceText(markdownTags[tag])));
					nodeList.push(markdownTags[tag]);
				}
				break;
			case "a":
				var text = sliceText("[");
				text = text.replace(/\s+/g, " ");
				text = trim(text);

				if (text == "") {
					nodeList.pop();
					break;
				}

				var attrs = linkAttrStack.pop();
				var url;
				attrs["href"] &&  attrs["href"].value != "" ? url = attrs["href"].value : url = "";

				if (url == "") {
					nodeList.pop();
					nodeList.push(text);
					break;
				}

				nodeList.push(text);

				if (!inlineStyle && !startsWith(peek(nodeList), "!")){
					var l = links.indexOf(url);
					if (l == -1) {
						links.push(url);
						l=links.length-1;
					}
					nodeList.push("][" + l + "]");
				} else {
					if(startsWith(peek(nodeList), "!")){
						var text = nodeList.pop();
						text = nodeList.pop() + text;
						block();
						nodeList.push(text);
					}

					var title = attrs["title"];
					nodeList.push("](" + url + (title ? " \"" + trim(title.value).replace(/\s+/g, " ") + "\"" : "") + ")");

					if(startsWith(peek(nodeList), "!")){
						block(true);
					}
				}
				break;
			case "ul":
			case "ol":
			case "dl":
				listBlock();
				listTagStack.pop();
				break;
			case "li":
			case "dt":
				var li = getListMarkdownTag();
				if (!removeIfEmptyTag(li)) {
					var text = trim(sliceText(li));

					if (startsWith(text, "[![")) {
						nodeList.pop();
						block();
						nodeList.push(text);
						block(true);
					} else {
						nodeList.push(text);
						listBlock();
					}
				}
				break;
			case "blockquote":
				blockquoteStack.pop();
				break;
			case "pre":
				//uncomment following experimental code to discard line numbers when syntax highlighters are used
				//notes this code thorough testing before production user
				/*
				var p=[];
				var flag = true;
				var count = 0, whiteSpace = 0, line = 0;
				console.log(">> " + peek(nodeList));
				while(peek(nodeList).startsWith("    ") || flag == true)
				{
					//console.log('inside');
					var text = nodeList.pop();
					p.push(text);

					if(flag == true && !text.startsWith("    ")) {
						continue;
					} else {
						flag = false;
					}

					//var result = parseInt(text.trim());
					if(!isNaN(text.trim())) {
						count++;
					} else if(text.trim() == ""){
						whiteSpace++;
					} else {
						line++;
					}
					flag = false;
				}

				console.log(line);
				if(line != 0)
				{
					while(p.length != 0) {
						nodeList.push(p.pop());
					}
				}
				*/
				block(true);
				preStack.pop();
				break;
			case "code":
			case "span":
				if (preStack.length > 0) {
					break;
				} else if (trim(peek(nodeList)) == "") {
					nodeList.pop();
					nodeList.push(markdownTags[tag]);
				} else {
					var text = nodeList.pop();
					nodeList.push(trim(text));
					nodeList.push(markdownTags[tag]);
				}
				break;
			case "table":
				nodeList.push("</table>");
				break;
			case "thead":
				nodeList.push("</thead>");
				break;
			case "tbody":
				nodeList.push("</tbody>");
				break;
			case "tr":
				nodeList.push("</tr>");
				break;
			case "td":
				nodeList.push("</td>");
				break;
			case "br":
			case "hr":
			case "img":
				break;
			}

		}
	}, {"nodesToIgnore": ["script", "noscript", "object", "iframe", "frame", "head", "style", "label"]});

	if (!inlineStyle) {
		for (var i = 0; i < links.length; i++) {
			if (i == 0) {
				var lastItem = nodeList.pop();
				nodeList.push(lastItem.replace(/\s+$/g, ""));
				nodeList.push("\n\n[" + i + "]: " + links[i]);
			} else {
				nodeList.push("\n[" + i + "]: " + links[i]);
			}
		}
	}

	return nodeList.join("");

}

return html2markdown;

});