why-cant-we-deploy-today/plugin/markdown/markdown.js

// From https://gist.github.com/1343518
// Modified by Hakim to handle Markdown indented with tabs
(function(){

	if( typeof marked === 'undefined' ) {
		throw 'The reveal.js Markdown plugin requires marked to be loaded';
	}

	if( typeof hljs !== 'undefined' ) {
		marked.setOptions({
			highlight: function( lang, code ) {
				return hljs.highlightAuto( lang, code ).value;
			}
		});
	}

	function stripLeadingWhitespace( section ) {

		var template = section.querySelector( 'script' );

		// strip leading whitespace so it isn't evaluated as code
		var text = ( template || section ).textContent;

		var leadingWs = text.match( /^\n?(\s*)/ )[1].length,
			leadingTabs = text.match( /^\n?(\t*)/ )[1].length;

		if( leadingTabs > 0 ) {
			text = text.replace( new RegExp('\\n?\\t{' + leadingTabs + '}','g'), '\n' );
		}
		else if( leadingWs > 1 ) {
			text = text.replace( new RegExp('\\n? {' + leadingWs + '}','g'), '\n' );
		}

		return text;

	};

	function twrap( el ) {

		var content = el.content || el;

		if( el.asideContent ) {
			content += '<aside class="notes" data-markdown>' + el.asideContent + '</aside>';
		}

		return '<script type="text/template">' + content + '</script>';

	};

	function getForwardedAttributes( section ) {

		var attributes = section.attributes;
		var result = [];

		for( var i = 0, len = attributes.length; i < len; i++ ) {
			var name = attributes[i].name,
				value = attributes[i].value;

			// disregard attributes that are used for markdown loading/parsing
			if( /data\-(markdown|separator|vertical|notes)/gi.test( name ) ) continue;

			if( value ) {
				result.push( name + '=' + value );
			}
			else {
				result.push( name );
			}
		}

		return result.join( ' ' );

	};

	function slidifyMarkdown( markdown, separator, vertical, notes, attributes ) {

		separator = separator || '^\n---\n$';
		notes = notes || 'note:';

		var separatorRegex = new RegExp( separator + ( vertical ? '|' + vertical : '' ), 'mg' ),
			horizontalSeparatorRegex = new RegExp( separator ),
			notesSeparatorRegex = new RegExp( notes, 'mgi' ),
			matches,
			noteMatch,
			lastIndex = 0,
			isHorizontal,
			wasHorizontal = true,
			content,
			asideContent,
			slide,
			sectionStack = [],
			markdownSections = '';

		// iterate until all blocks between separators are stacked up
		while( matches = separatorRegex.exec( markdown ) ) {
			asideContent = null;

			// determine direction (horizontal by default)
			isHorizontal = horizontalSeparatorRegex.test( matches[0] );

			if( !isHorizontal && wasHorizontal ) {
				// create vertical stack
				sectionStack.push( [] );
			}

			// pluck slide content from markdown input
			content = markdown.substring( lastIndex, matches.index );
			noteMatch = content.split( notesSeparatorRegex );

			if( noteMatch.length === 2 ) {
				content = noteMatch[0];
				asideContent = noteMatch[1].trim();
			}

			slide = {
				content: content,
				asideContent: asideContent || ''
			};

			if( isHorizontal && wasHorizontal ) {
				// add to horizontal stack
				sectionStack.push(slide);
			} else {
				// add to vertical stack
				sectionStack[sectionStack.length-1].push(slide);
			}

			lastIndex = separatorRegex.lastIndex;
			wasHorizontal = isHorizontal;
		}

		// add the remaining slide
		(wasHorizontal ? sectionStack : sectionStack[sectionStack.length-1]).push(markdown.substring(lastIndex));

		// flatten the hierarchical stack, and insert <section data-markdown> tags
		for( var k = 0, klen = sectionStack.length; k < klen; k++ ) {
			// vertical
			if( sectionStack[k].propertyIsEnumerable( length ) && typeof sectionStack[k].splice === 'function' ) {
				markdownSections += '<section '+ attributes +'>' +
										'<section data-markdown>' +  sectionStack[k].map( twrap ).join( '</section><section data-markdown>' ) + '</section>' +
									'</section>';
			} else {
				markdownSections += '<section '+ attributes +' data-markdown>' + twrap( sectionStack[k] ) + '</section>';
			}
		}

		return markdownSections;
	};

	function queryExternalMarkdown() {

		var sections = document.querySelectorAll( '[data-markdown]'),
			section;

		for( var j = 0, jlen = sections.length; j < jlen; j++ ) {

			section = sections[j];

			if( section.getAttribute( 'data-markdown' ).length ) {

				var xhr = new XMLHttpRequest(),
					url = section.getAttribute( 'data-markdown' );

				datacharset = section.getAttribute( 'data-charset' );

				// see https://developer.mozilla.org/en-US/docs/Web/API/element.getAttribute#Notes
				if( datacharset != null && datacharset != '' ) {
					xhr.overrideMimeType( 'text/html; charset=' + datacharset );
				}

				xhr.onreadystatechange = function() {
					if( xhr.readyState === 4 ) {
						if ( xhr.status >= 200 && xhr.status < 300 ) {
							section.outerHTML = slidifyMarkdown( xhr.responseText, section.getAttribute( 'data-separator' ), section.getAttribute( 'data-vertical' ), section.getAttribute( 'data-notes' ), getForwardedAttributes( section ) );
						}
						else {
							section.outerHTML = '<section data-state="alert">ERROR: The attempt to fetch ' + url + ' failed with the HTTP status ' + xhr.status +
								'. Check your browser\'s JavaScript console for more details.' +
								'<p>Remember that you need to serve the presentation HTML from a HTTP server and the Markdown file must be there too.</p></section>';
						}
					}
				};

				xhr.open( 'GET', url, false );

				try {
					xhr.send();
				}
				catch ( e ) {
					alert( 'Failed to get the Markdown file ' + url + '. Make sure that the presentation and the file are served by a HTTP server and the file can be found there. ' + e );
				}

			} else if( section.getAttribute( 'data-separator' ) ) {

				var markdown = stripLeadingWhitespace( section );
				section.outerHTML = slidifyMarkdown( markdown, section.getAttribute( 'data-separator' ), section.getAttribute( 'data-vertical' ), section.getAttribute( 'data-notes' ), getForwardedAttributes( section ) );

			}
		}

	};

	function queryMarkdownSlides() {

		var sections = document.querySelectorAll( '[data-markdown]');

		for( var j = 0, jlen = sections.length; j < jlen; j++ ) {

			makeHtml( sections[j] );

		}

	};

	function makeHtml( section ) {

		var notes = section.querySelector( 'aside.notes' );

		var markdown = stripLeadingWhitespace( section );

		section.innerHTML = marked( markdown );

		if( notes ) {
			section.appendChild( notes );
		}

	};

	queryExternalMarkdown();
	queryMarkdownSlides();

})();