inst/reveal.js-5.1.0/plugin/markdown/plugin.js - IDS-Mannheim/revealjs - Gitiles

 /*!
  * The reveal.js markdown plugin. Handles parsing of
  * markdown inside of presentations as well as loading
  * of external markdown documents.
  */

 import { marked } from 'marked';

 const DEFAULT_SLIDE_SEPARATOR = '\r?\n---\r?\n',
 	  DEFAULT_VERTICAL_SEPARATOR = null,
 	  DEFAULT_NOTES_SEPARATOR = '^\s*notes?:',
 	  DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR = '\\\.element\\\s*?(.+?)$',
 	  DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR = '\\\.slide:\\\s*?(\\\S.+?)$';

 const SCRIPT_END_PLACEHOLDER = '__SCRIPT_END__';

 // match an optional line number offset and highlight line numbers
 // [<line numbers>] or [<offset>: <line numbers>]
 const CODE_LINE_NUMBER_REGEX = /\[\s*((\d*):)?\s*([\s\d,|-]*)\]/;

 const HTML_ESCAPE_MAP = {
   '&': '&amp;',
   '<': '&lt;',
   '>': '&gt;',
   '"': '&quot;',
   "'": '&#39;'
 };

 const Plugin = () => {

 	// The reveal.js instance this plugin is attached to
 	let deck;

 	/**
 	 * Retrieves the markdown contents of a slide section
 	 * element. Normalizes leading tabs/whitespace.
 	 */
 	function getMarkdownFromSlide( section ) {

 		// look for a <script> or <textarea data-template> wrapper
 		const template = section.querySelector( '[data-template]' ) || section.querySelector( 'script' );

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

 		// restore script end tags
 		text = text.replace( new RegExp( SCRIPT_END_PLACEHOLDER, 'g' ), '</script>' );

 		const 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'), function(m, p1) { return '\n' + p1 ; } );
 		}
 		else if( leadingWs > 1 ) {
 			text = text.replace( new RegExp('\\n? {' + leadingWs + '}(.*)', 'g'), function(m, p1) { return '\n' + p1 ; } );
 		}

 		return text;

 	}

 	/**
 	 * Given a markdown slide section element, this will
 	 * return all arguments that aren't related to markdown
 	 * parsing. Used to forward any other user-defined arguments
 	 * to the output markdown slide.
 	 */
 	function getForwardedAttributes( section ) {

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

 		for( let i = 0, len = attributes.length; i < len; i++ ) {
 			const 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( ' ' );

 	}

 	/**
 	 * Inspects the given options and fills out default
 	 * values for what's not defined.
 	 */
 	function getSlidifyOptions( options ) {
 		const markdownConfig = deck?.getConfig?.().markdown;

 		options = options || {};
 		options.separator = options.separator || markdownConfig?.separator || DEFAULT_SLIDE_SEPARATOR;
 		options.verticalSeparator = options.verticalSeparator || markdownConfig?.verticalSeparator || DEFAULT_VERTICAL_SEPARATOR;
 		options.notesSeparator = options.notesSeparator || markdownConfig?.notesSeparator || DEFAULT_NOTES_SEPARATOR;
 		options.attributes = options.attributes || '';

 		return options;

 	}

 	/**
 	 * Helper function for constructing a markdown slide.
 	 */
 	function createMarkdownSlide( content, options ) {

 		options = getSlidifyOptions( options );

 		const notesMatch = content.split( new RegExp( options.notesSeparator, 'mgi' ) );

 		if( notesMatch.length === 2 ) {
 			content = notesMatch[0] + '<aside class="notes">' + marked(notesMatch[1].trim()) + '</aside>';
 		}

 		// prevent script end tags in the content from interfering
 		// with parsing
 		content = content.replace( /<\/script>/g, SCRIPT_END_PLACEHOLDER );

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

 	}

 	/**
 	 * Parses a data string into multiple slides based
 	 * on the passed in separator arguments.
 	 */
 	function slidify( markdown, options ) {

 		options = getSlidifyOptions( options );

 		const separatorRegex = new RegExp( options.separator + ( options.verticalSeparator ? '|' + options.verticalSeparator : '' ), 'mg' ),
 			horizontalSeparatorRegex = new RegExp( options.separator );

 		let matches,
 			lastIndex = 0,
 			isHorizontal,
 			wasHorizontal = true,
 			content,
 			sectionStack = [];

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

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

 			lastIndex = separatorRegex.lastIndex;
 			wasHorizontal = isHorizontal;
 		}

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

 		let markdownSections = '';

 		// flatten the hierarchical stack, and insert <section data-markdown> tags
 		for( let i = 0, len = sectionStack.length; i < len; i++ ) {
 			// vertical
 			if( sectionStack[i] instanceof Array ) {
 				markdownSections += '<section '+ options.attributes +'>';

 				sectionStack[i].forEach( function( child ) {
 					markdownSections += '<section data-markdown>' + createMarkdownSlide( child, options ) + '</section>';
 				} );

 				markdownSections += '</section>';
 			}
 			else {
 				markdownSections += '<section '+ options.attributes +' data-markdown>' + createMarkdownSlide( sectionStack[i], options ) + '</section>';
 			}
 		}

 		return markdownSections;

 	}

 	/**
 	 * Parses any current data-markdown slides, splits
 	 * multi-slide markdown into separate sections and
 	 * handles loading of external markdown.
 	 */
 	function processSlides( scope ) {

 		return new Promise( function( resolve ) {

 			const externalPromises = [];

 			[].slice.call( scope.querySelectorAll( 'section[data-markdown]:not([data-markdown-parsed])') ).forEach( function( section, i ) {

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

 					externalPromises.push( loadExternalMarkdown( section ).then(

 						// Finished loading external file
 						function( xhr, url ) {
 							section.outerHTML = slidify( xhr.responseText, {
 								separator: section.getAttribute( 'data-separator' ),
 								verticalSeparator: section.getAttribute( 'data-separator-vertical' ),
 								notesSeparator: section.getAttribute( 'data-separator-notes' ),
 								attributes: getForwardedAttributes( section )
 							});
 						},

 						// Failed to load markdown
 						function( xhr, url ) {
 							section.outerHTML = '<section data-state="alert">' +
 								'ERROR: The attempt to fetch ' + url + ' failed with 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.</p>' +
 								'</section>';
 						}

 					) );

 				}
 				else {

 					section.outerHTML = slidify( getMarkdownFromSlide( section ), {
 						separator: section.getAttribute( 'data-separator' ),
 						verticalSeparator: section.getAttribute( 'data-separator-vertical' ),
 						notesSeparator: section.getAttribute( 'data-separator-notes' ),
 						attributes: getForwardedAttributes( section )
 					});

 				}

 			});

 			Promise.all( externalPromises ).then( resolve );

 		} );

 	}

 	function loadExternalMarkdown( section ) {

 		return new Promise( function( resolve, reject ) {

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

 			const 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( section, xhr ) {
 				if( xhr.readyState === 4 ) {
 					// file protocol yields status code 0 (useful for local debug, mobile applications etc.)
 					if ( ( xhr.status >= 200 && xhr.status < 300 ) || xhr.status === 0 ) {

 						resolve( xhr, url );

 					}
 					else {

 						reject( xhr, url );

 					}
 				}
 			}.bind( this, section, xhr );

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

 			try {
 				xhr.send();
 			}
 			catch ( e ) {
 				console.warn( '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 );
 				resolve( xhr, url );
 			}

 		} );

 	}

 	/**
 	 * Check if a node value has the attributes pattern.
 	 * If yes, extract it and add that value as one or several attributes
 	 * to the target element.
 	 *
 	 * You need Cache Killer on Chrome to see the effect on any FOM transformation
 	 * directly on refresh (F5)
 	 * http://stackoverflow.com/questions/5690269/disabling-chrome-cache-for-website-development/7000899#answer-11786277
 	 */
 	function addAttributeInElement( node, elementTarget, separator ) {

 		const markdownClassesInElementsRegex = new RegExp( separator, 'mg' );
 		const markdownClassRegex = new RegExp( "([^\"= ]+?)=\"([^\"]+?)\"|(data-[^\"= ]+?)(?=[\" ])", 'mg' );
 		let nodeValue = node.nodeValue;
 		let matches,
 			matchesClass;
 		if( matches = markdownClassesInElementsRegex.exec( nodeValue ) ) {

 			const classes = matches[1];
 			nodeValue = nodeValue.substring( 0, matches.index ) + nodeValue.substring( markdownClassesInElementsRegex.lastIndex );
 			node.nodeValue = nodeValue;
 			while( matchesClass = markdownClassRegex.exec( classes ) ) {
 				if( matchesClass[2] ) {
 					elementTarget.setAttribute( matchesClass[1], matchesClass[2] );
 				} else {
 					elementTarget.setAttribute( matchesClass[3], "" );
 				}
 			}
 			return true;
 		}
 		return false;
 	}

 	/**
 	 * Add attributes to the parent element of a text node,
 	 * or the element of an attribute node.
 	 */
 	function addAttributes( section, element, previousElement, separatorElementAttributes, separatorSectionAttributes ) {

 		if ( element !== null && element.childNodes !== undefined && element.childNodes.length > 0 ) {
 			let previousParentElement = element;
 			for( let i = 0; i < element.childNodes.length; i++ ) {
 				const childElement = element.childNodes[i];
 				if ( i > 0 ) {
 					let j = i - 1;
 					while ( j >= 0 ) {
 						const aPreviousChildElement = element.childNodes[j];
 						if ( typeof aPreviousChildElement.setAttribute === 'function' && aPreviousChildElement.tagName !== "BR" ) {
 							previousParentElement = aPreviousChildElement;
 							break;
 						}
 						j = j - 1;
 					}
 				}
 				let parentSection = section;
 				if( childElement.nodeName ===  "section" ) {
 					parentSection = childElement ;
 					previousParentElement = childElement ;
 				}
 				if ( typeof childElement.setAttribute === 'function' || childElement.nodeType === Node.COMMENT_NODE ) {
 					addAttributes( parentSection, childElement, previousParentElement, separatorElementAttributes, separatorSectionAttributes );
 				}
 			}
 		}

 		if ( element.nodeType === Node.COMMENT_NODE ) {
 			if ( addAttributeInElement( element, previousElement, separatorElementAttributes ) === false ) {
 				addAttributeInElement( element, section, separatorSectionAttributes );
 			}
 		}
 	}

 	/**
 	 * Converts any current data-markdown slides in the
 	 * DOM to HTML.
 	 */
 	function convertSlides() {

 		const sections = deck.getRevealElement().querySelectorAll( '[data-markdown]:not([data-markdown-parsed])');

 		[].slice.call( sections ).forEach( function( section ) {

 			section.setAttribute( 'data-markdown-parsed', true )

 			const notes = section.querySelector( 'aside.notes' );
 			const markdown = getMarkdownFromSlide( section );

 			section.innerHTML = marked( markdown );
 			addAttributes( 	section, section, null, section.getAttribute( 'data-element-attributes' ) ||
 							section.parentNode.getAttribute( 'data-element-attributes' ) ||
 							DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR,
 							section.getAttribute( 'data-attributes' ) ||
 							section.parentNode.getAttribute( 'data-attributes' ) ||
 							DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR);

 			// If there were notes, we need to re-add them after
 			// having overwritten the section's HTML
 			if( notes ) {
 				section.appendChild( notes );
 			}

 		} );

 		return Promise.resolve();

 	}

 	function escapeForHTML( input ) {

 	  return input.replace( /([&<>'"])/g, char => HTML_ESCAPE_MAP[char] );

 	}

 	return {
 		id: 'markdown',

 		/**
 		 * Starts processing and converting Markdown within the
 		 * current reveal.js deck.
 		 */
 		init: function( reveal ) {

 			deck = reveal;

 			let { renderer, animateLists, ...markedOptions } = deck.getConfig().markdown || {};

 			if( !renderer ) {
 				renderer = new marked.Renderer();

 				renderer.code = ( code, language ) => {

 					// Off by default
 					let lineNumberOffset = '';
 					let lineNumbers = '';

 					// Users can opt in to show line numbers and highlight
 					// specific lines.
 					// ```javascript []        show line numbers
 					// ```javascript [1,4-8]   highlights lines 1 and 4-8
 					// optional line number offset:
 					// ```javascript [25: 1,4-8]   start line numbering at 25,
 					//                             highlights lines 1 (numbered as 25) and 4-8 (numbered as 28-32)
 					if( CODE_LINE_NUMBER_REGEX.test( language ) ) {
 						let lineNumberOffsetMatch =  language.match( CODE_LINE_NUMBER_REGEX )[2];
 						if (lineNumberOffsetMatch){
 							lineNumberOffset =  `data-ln-start-from="${lineNumberOffsetMatch.trim()}"`;
 						}

 						lineNumbers = language.match( CODE_LINE_NUMBER_REGEX )[3].trim();
 						lineNumbers = `data-line-numbers="${lineNumbers}"`;
 						language = language.replace( CODE_LINE_NUMBER_REGEX, '' ).trim();
 					}

 					// Escape before this gets injected into the DOM to
 					// avoid having the HTML parser alter our code before
 					// highlight.js is able to read it
 					code = escapeForHTML( code );

 					// return `<pre><code ${lineNumbers} class="${language}">${code}</code></pre>`;

 					return `<pre><code ${lineNumbers} ${lineNumberOffset} class="${language}">${code}</code></pre>`;
 				};
 			}

 			if( animateLists === true ) {
 				renderer.listitem = text => `<li class="fragment">${text}</li>`;
 			}

 			marked.setOptions( {
 				renderer,
 				...markedOptions
 			} );

 			return processSlides( deck.getRevealElement() ).then( convertSlides );

 		},

 		// TODO: Do these belong in the API?
 		processSlides: processSlides,
 		convertSlides: convertSlides,
 		slidify: slidify,
 		marked: marked
 	}

 };

 export default Plugin;
	/*!
	* The reveal.js markdown plugin. Handles parsing of
	* markdown inside of presentations as well as loading
	* of external markdown documents.
	*/

	import { marked } from 'marked';

	const DEFAULT_SLIDE_SEPARATOR = '\r?\n---\r?\n',
	DEFAULT_VERTICAL_SEPARATOR = null,
	DEFAULT_NOTES_SEPARATOR = '^\s*notes?:',
	DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR = '\\\.element\\\s*?(.+?)$',
	DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR = '\\\.slide:\\\s*?(\\\S.+?)$';

	const SCRIPT_END_PLACEHOLDER = '__SCRIPT_END__';

	// match an optional line number offset and highlight line numbers
	// [<line numbers>] or [<offset>: <line numbers>]
	const CODE_LINE_NUMBER_REGEX = /\[\s((\d):)?\s([\s\d,\|-])\]/;

	const HTML_ESCAPE_MAP = {
	'&': '&',
	'<': '<',
	'>': '>',
	'"': '"',
	"'": '''
	};

	const Plugin = () => {

	// The reveal.js instance this plugin is attached to
	let deck;

	/**
	* Retrieves the markdown contents of a slide section
	* element. Normalizes leading tabs/whitespace.
	*/
	function getMarkdownFromSlide( section ) {

	// look for a <script> or <textarea data-template> wrapper
	const template = section.querySelector( '[data-template]' ) \|\| section.querySelector( 'script' );

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

	// restore script end tags
	text = text.replace( new RegExp( SCRIPT_END_PLACEHOLDER, 'g' ), '</script>' );

	const 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'), function(m, p1) { return '\n' + p1 ; } );
	}
	else if( leadingWs > 1 ) {
	text = text.replace( new RegExp('\\n? {' + leadingWs + '}(.*)', 'g'), function(m, p1) { return '\n' + p1 ; } );
	}

	return text;

	}

	/**
	* Given a markdown slide section element, this will
	* return all arguments that aren't related to markdown
	* parsing. Used to forward any other user-defined arguments
	* to the output markdown slide.
	*/
	function getForwardedAttributes( section ) {

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

	for( let i = 0, len = attributes.length; i < len; i++ ) {
	const 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( ' ' );

	}

	/**
	* Inspects the given options and fills out default
	* values for what's not defined.
	*/
	function getSlidifyOptions( options ) {
	const markdownConfig = deck?.getConfig?.().markdown;

	options = options \|\| {};
	options.separator = options.separator \|\| markdownConfig?.separator \|\| DEFAULT_SLIDE_SEPARATOR;
	options.verticalSeparator = options.verticalSeparator \|\| markdownConfig?.verticalSeparator \|\| DEFAULT_VERTICAL_SEPARATOR;
	options.notesSeparator = options.notesSeparator \|\| markdownConfig?.notesSeparator \|\| DEFAULT_NOTES_SEPARATOR;
	options.attributes = options.attributes \|\| '';

	return options;

	}

	/**
	* Helper function for constructing a markdown slide.
	*/
	function createMarkdownSlide( content, options ) {

	options = getSlidifyOptions( options );

	const notesMatch = content.split( new RegExp( options.notesSeparator, 'mgi' ) );

	if( notesMatch.length === 2 ) {
	content = notesMatch[0] + '<aside class="notes">' + marked(notesMatch[1].trim()) + '</aside>';
	}

	// prevent script end tags in the content from interfering
	// with parsing
	content = content.replace( /<\/script>/g, SCRIPT_END_PLACEHOLDER );

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

	}

	/**
	* Parses a data string into multiple slides based
	* on the passed in separator arguments.
	*/
	function slidify( markdown, options ) {

	options = getSlidifyOptions( options );

	const separatorRegex = new RegExp( options.separator + ( options.verticalSeparator ? '\|' + options.verticalSeparator : '' ), 'mg' ),
	horizontalSeparatorRegex = new RegExp( options.separator );

	let matches,
	lastIndex = 0,
	isHorizontal,
	wasHorizontal = true,
	content,
	sectionStack = [];

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

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

	lastIndex = separatorRegex.lastIndex;
	wasHorizontal = isHorizontal;
	}

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

	let markdownSections = '';

	// flatten the hierarchical stack, and insert <section data-markdown> tags
	for( let i = 0, len = sectionStack.length; i < len; i++ ) {
	// vertical
	if( sectionStack[i] instanceof Array ) {
	markdownSections += '<section '+ options.attributes +'>';

	sectionStack[i].forEach( function( child ) {
	markdownSections += '<section data-markdown>' + createMarkdownSlide( child, options ) + '</section>';
	} );

	markdownSections += '</section>';
	}
	else {
	markdownSections += '<section '+ options.attributes +' data-markdown>' + createMarkdownSlide( sectionStack[i], options ) + '</section>';
	}
	}

	return markdownSections;

	}

	/**
	* Parses any current data-markdown slides, splits
	* multi-slide markdown into separate sections and
	* handles loading of external markdown.
	*/
	function processSlides( scope ) {

	return new Promise( function( resolve ) {

	const externalPromises = [];

	[].slice.call( scope.querySelectorAll( 'section[data-markdown]:not([data-markdown-parsed])') ).forEach( function( section, i ) {

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

	externalPromises.push( loadExternalMarkdown( section ).then(

	// Finished loading external file
	function( xhr, url ) {
	section.outerHTML = slidify( xhr.responseText, {
	separator: section.getAttribute( 'data-separator' ),
	verticalSeparator: section.getAttribute( 'data-separator-vertical' ),
	notesSeparator: section.getAttribute( 'data-separator-notes' ),
	attributes: getForwardedAttributes( section )
	});
	},

	// Failed to load markdown
	function( xhr, url ) {
	section.outerHTML = '<section data-state="alert">' +
	'ERROR: The attempt to fetch ' + url + ' failed with 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.</p>' +
	'</section>';
	}

	) );

	}
	else {

	section.outerHTML = slidify( getMarkdownFromSlide( section ), {
	separator: section.getAttribute( 'data-separator' ),
	verticalSeparator: section.getAttribute( 'data-separator-vertical' ),
	notesSeparator: section.getAttribute( 'data-separator-notes' ),
	attributes: getForwardedAttributes( section )
	});

	}

	});

	Promise.all( externalPromises ).then( resolve );

	} );

	}

	function loadExternalMarkdown( section ) {

	return new Promise( function( resolve, reject ) {

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

	const 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( section, xhr ) {
	if( xhr.readyState === 4 ) {
	// file protocol yields status code 0 (useful for local debug, mobile applications etc.)
	if ( ( xhr.status >= 200 && xhr.status < 300 ) \|\| xhr.status === 0 ) {

	resolve( xhr, url );

	}
	else {

	reject( xhr, url );

	}
	}
	}.bind( this, section, xhr );

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

	try {
	xhr.send();
	}
	catch ( e ) {
	console.warn( '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 );
	resolve( xhr, url );
	}

	} );

	}

	/**
	* Check if a node value has the attributes pattern.
	* If yes, extract it and add that value as one or several attributes
	* to the target element.
	*
	* You need Cache Killer on Chrome to see the effect on any FOM transformation
	* directly on refresh (F5)
	* http://stackoverflow.com/questions/5690269/disabling-chrome-cache-for-website-development/7000899#answer-11786277
	*/
	function addAttributeInElement( node, elementTarget, separator ) {

	const markdownClassesInElementsRegex = new RegExp( separator, 'mg' );
	const markdownClassRegex = new RegExp( "([^\"= ]+?)=\"([^\"]+?)\"\|(data-[^\"= ]+?)(?=[\" ])", 'mg' );
	let nodeValue = node.nodeValue;
	let matches,
	matchesClass;
	if( matches = markdownClassesInElementsRegex.exec( nodeValue ) ) {

	const classes = matches[1];
	nodeValue = nodeValue.substring( 0, matches.index ) + nodeValue.substring( markdownClassesInElementsRegex.lastIndex );
	node.nodeValue = nodeValue;
	while( matchesClass = markdownClassRegex.exec( classes ) ) {
	if( matchesClass[2] ) {
	elementTarget.setAttribute( matchesClass[1], matchesClass[2] );
	} else {
	elementTarget.setAttribute( matchesClass[3], "" );
	}
	}
	return true;
	}
	return false;
	}

	/**
	* Add attributes to the parent element of a text node,
	* or the element of an attribute node.
	*/
	function addAttributes( section, element, previousElement, separatorElementAttributes, separatorSectionAttributes ) {

	if ( element !== null && element.childNodes !== undefined && element.childNodes.length > 0 ) {
	let previousParentElement = element;
	for( let i = 0; i < element.childNodes.length; i++ ) {
	const childElement = element.childNodes[i];
	if ( i > 0 ) {
	let j = i - 1;
	while ( j >= 0 ) {
	const aPreviousChildElement = element.childNodes[j];
	if ( typeof aPreviousChildElement.setAttribute === 'function' && aPreviousChildElement.tagName !== "BR" ) {
	previousParentElement = aPreviousChildElement;
	break;
	}
	j = j - 1;
	}
	}
	let parentSection = section;
	if( childElement.nodeName === "section" ) {
	parentSection = childElement ;
	previousParentElement = childElement ;
	}
	if ( typeof childElement.setAttribute === 'function' \|\| childElement.nodeType === Node.COMMENT_NODE ) {
	addAttributes( parentSection, childElement, previousParentElement, separatorElementAttributes, separatorSectionAttributes );
	}
	}
	}

	if ( element.nodeType === Node.COMMENT_NODE ) {
	if ( addAttributeInElement( element, previousElement, separatorElementAttributes ) === false ) {
	addAttributeInElement( element, section, separatorSectionAttributes );
	}
	}
	}

	/**
	* Converts any current data-markdown slides in the
	* DOM to HTML.
	*/
	function convertSlides() {

	const sections = deck.getRevealElement().querySelectorAll( '[data-markdown]:not([data-markdown-parsed])');

	[].slice.call( sections ).forEach( function( section ) {

	section.setAttribute( 'data-markdown-parsed', true )

	const notes = section.querySelector( 'aside.notes' );
	const markdown = getMarkdownFromSlide( section );

	section.innerHTML = marked( markdown );
	addAttributes( section, section, null, section.getAttribute( 'data-element-attributes' ) \|\|
	section.parentNode.getAttribute( 'data-element-attributes' ) \|\|
	DEFAULT_ELEMENT_ATTRIBUTES_SEPARATOR,
	section.getAttribute( 'data-attributes' ) \|\|
	section.parentNode.getAttribute( 'data-attributes' ) \|\|
	DEFAULT_SLIDE_ATTRIBUTES_SEPARATOR);

	// If there were notes, we need to re-add them after
	// having overwritten the section's HTML
	if( notes ) {
	section.appendChild( notes );
	}

	} );

	return Promise.resolve();

	}

	function escapeForHTML( input ) {

	return input.replace( /([&<>'"])/g, char => HTML_ESCAPE_MAP[char] );

	}

	return {
	id: 'markdown',

	/**
	* Starts processing and converting Markdown within the
	* current reveal.js deck.
	*/
	init: function( reveal ) {

	deck = reveal;

	let { renderer, animateLists, ...markedOptions } = deck.getConfig().markdown \|\| {};

	if( !renderer ) {
	renderer = new marked.Renderer();

	renderer.code = ( code, language ) => {

	// Off by default
	let lineNumberOffset = '';
	let lineNumbers = '';

	// Users can opt in to show line numbers and highlight
	// specific lines.
	// ```javascript [] show line numbers
	// ```javascript [1,4-8] highlights lines 1 and 4-8
	// optional line number offset:
	// ```javascript [25: 1,4-8] start line numbering at 25,
	// highlights lines 1 (numbered as 25) and 4-8 (numbered as 28-32)
	if( CODE_LINE_NUMBER_REGEX.test( language ) ) {
	let lineNumberOffsetMatch = language.match( CODE_LINE_NUMBER_REGEX )[2];
	if (lineNumberOffsetMatch){
	lineNumberOffset = `data-ln-start-from="${lineNumberOffsetMatch.trim()}"`;
	}

	lineNumbers = language.match( CODE_LINE_NUMBER_REGEX )[3].trim();
	lineNumbers = `data-line-numbers="${lineNumbers}"`;
	language = language.replace( CODE_LINE_NUMBER_REGEX, '' ).trim();
	}

	// Escape before this gets injected into the DOM to
	// avoid having the HTML parser alter our code before
	// highlight.js is able to read it
	code = escapeForHTML( code );

	// return `<pre><code ${lineNumbers} class="${language}">${code}</code></pre>`;

	return `<pre><code ${lineNumbers} ${lineNumberOffset} class="${language}">${code}</code></pre>`;
	};
	}

	if( animateLists === true ) {
	renderer.listitem = text => `<li class="fragment">${text}</li>`;
	}

	marked.setOptions( {
	renderer,
	...markedOptions
	} );

	return processSlides( deck.getRevealElement() ).then( convertSlides );

	},

	// TODO: Do these belong in the API?
	processSlides: processSlides,
	convertSlides: convertSlides,
	slidify: slidify,
	marked: marked
	}

	};

	export default Plugin;