plugin/markdown/plugin.js
/*!
* 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;