A Markdown to HTML converter written in Javascript
npm install devextreme-showdown![DevExtreme Showdown][sd-logo]
------
Showdown is a Javascript Markdown to HTML converter, based on the original works by John Gruber.
Showdown can be used client side (in the browser) or server side (with NodeJs).
This fork was created to fix the CVE-2020-7774 vulnerability and keep dependencies up to date
1.0.0.
js
var showdown = require('devextreme-showdown'),
converter = new showdown.Converter(),
text = '# hello, markdown!',
html = converter.makeHtml(text);
`
$3
`js
var converter = new showdown.Converter(),
text = '# hello, markdown!',
html = converter.makeHtml(text);
`
$3
Both examples should output...
`html
hello, markdown!
`
Options
You can change some of showdown's default behavior through options.
$3
Options can be set:
#### Globally
Setting a "global" option affects all instances of showdown
`js
showdown.setOption('optionKey', 'value');
`
#### Locally
Setting a "local" option only affects the specified Converter object.
Local options can be set:
* through the constructor
`js
var converter = new showdown.Converter({optionKey: 'value'});
`
* through the setOption() method
`js
var converter = new showdown.Converter();
converter.setOption('optionKey', 'value');
`
$3
Showdown provides 2 methods (both local and global) to retrieve previous set options.
#### getOption()
`js
// Global
var myOption = showdown.getOption('optionKey');
//Local
var myOption = converter.getOption('optionKey');
`
#### getOptions()
`js
// Global
var showdownGlobalOptions = showdown.getOptions();
//Local
var thisConverterSpecificOptions = converter.getOptions();
`
$3
You can get showdown's default options with:
`js
var defaultOptions = showdown.getDefaultOptions();
`
$3
* omitExtraWLInCodeBlocks: (boolean) [default false] Omit the trailing newline in a code block. Ex:
This:
`html
var foo = 'bar';
`
Becomes this:
`html
var foo = 'bar';
`
* noHeaderId: (boolean) [default false] Disable the automatic generation of header ids.
Setting to true overrides prefixHeaderId
* customizedHeaderId: (boolean) [default false] Use text in curly braces as header id. (since v1.7.0)
Example:
`
## Sample header {real-id} will use real-id as id
`
* ghCompatibleHeaderId: (boolean) [default false] Generate header ids compatible with github style
(spaces are replaced with dashes and a bunch of non alphanumeric chars are removed) (since v1.5.5)
* prefixHeaderId: (string/boolean) [default false] Add a prefix to the generated header ids.
Passing a string will prefix that string to the header id. Setting to true will add a generic 'section' prefix.
* rawPrefixHeaderId: (boolean) [default false] Setting this option to true will prevent showdown from modifying the prefix.
This might result in malformed IDs (if, for instance, the " char is used in the prefix).
Has no effect if prefixHeaderId is set to false. (since v 1.7.3)
* rawHeaderId: (boolean) [default false] Remove only spaces, ' and " from generated header ids (including prefixes),
replacing them with dashes (-). WARNING: This might result in malformed ids (since v1.7.3)
* headerLevelStart: (integer) [default 1] Set the header starting level. For instance, setting this to 3 means that
`md
# foo
`
will be parsed as
`html
foo
`
* parseImgDimensions: (boolean) [default false] Enable support for setting image dimensions from within markdown syntax.
Examples:
`
!foo simple, assumes units are in px
!bar sets the height to "auto"
!baz Image with width of 80% and height of 5em
`
* simplifiedAutoLink: (boolean) [default false] Turning this option on will enable automatic linking to urls.
This means that:
`md
some text www.google.com
`
will be parsed as
`html
some text www.google.com
`
* ~~excludeTrailingPunctuationFromURLs: (boolean) [default false] This option excludes trailing punctuation from autolinking urls.
Punctuation excluded: . ! ? ( ). Only applies if simplifiedAutoLink option is set to true.~~
* literalMidWordUnderscores: (boolean) [default false] Turning this on will stop showdown from interpreting
underscores in the middle of words as and and instead treat them as literal underscores.
Example:
`md
some text with__underscores__in middle
`
will be parsed as
`html
some text with__underscores__in middle
`
* ~~literalMidWordAsterisks: (boolean) [default false] Turning this on will stop showdown from interpreting asterisks
in the middle of words as and and instead treat them as literal asterisks.~~
* strikethrough: (boolean) [default false] Enable support for strikethrough syntax.
~~strikethrough~~ as
* tables: (boolean) [default false] Enable support for tables syntax. Example:
`md
| h1 | h2 | h3 |
|:------|:-------:|--------:|
| 100 | [a][1] | ![b][2] |
| foo | bar | ~~baz~~ |
`
See the wiki for more info
* tablesHeaderId: (boolean) [default false] If enabled adds an id property to table headers tags.
* ghCodeBlocks: (boolean) [default true] Enable support for GFM code block style.
* tasklists: (boolean) [default false] Enable support for GFM tasklists. Example:
`md
- [x] This task is done
- [ ] This is still pending
`
* smoothLivePreview: (boolean) [default false] Prevents weird effects in live previews due to incomplete input
* smartIndentationFix: (boolean) [default false] Tries to smartly fix indentation problems related to es6 template
strings in the midst of indented code.
* disableForced4SpacesIndentedSublists: (boolean) [default false] Disables the requirement of indenting sublists
by 4 spaces for them to be nested, effectively reverting to the old behavior where 2 or 3 spaces were enough.
(since v1.5.0)
* simpleLineBreaks: (boolean) [default false] Parses line breaks as , without
needing 2 spaces at the end of the line (since v1.5.1)
`md
a line
wrapped in two
`
turns into:
`html
a line
wrapped in two
`
* requireSpaceBeforeHeadingText: (boolean) [default false] Makes adding a space between # and the header text mandatory (since v1.5.3)
* ghMentions: (boolean) [default false] Enables github @mentions, which link to the username mentioned (since v1.6.0)
* ghMentionsLink: (string) [default https://github.com/{u}] Changes the link generated by @mentions.
Showdown will replace {u} with the username. Only applies if ghMentions option is enabled.
Example: @tivie with ghMentionsOption set to //mysite.com/{u}/profile will result in @tivie
* encodeEmails: (boolean) [default true] Enable e-mail addresses encoding through the use of Character Entities, transforming ASCII e-mail addresses into its equivalent decimal entities. (since v1.6.1)
NOTE: Prior to version 1.6.1, emails would always be obfuscated through dec and hex encoding.
* openLinksInNewWindow: (boolean) [default false] Open all links in new windows
(by adding the attribute target="_blank" to tags) (since v1.7.0)
* backslashEscapesHTMLTags: (boolean) [default false] Support for HTML Tag escaping. ex: \ (since v1.7.2)
* emoji: (boolean) [default false] Enable emoji support. Ex: this is a :smile: emoji
For more info on available emojis, see https://github.com/showdownjs/showdown/wiki/Emojis (since v.1.8.0)
underline: (boolean) [default false] EXPERIMENTAL FEATURE* Enable support for underline.
. With this option enabled, underscores are no longer parses into and .
* completeHTMLDocument: (boolean) [default false] Outputs a complete html document,
including , and tags' instead of an HTML fragment. (since v.1.8.5)
* metadata: (boolean) [default false] Enable support for document metadata (defined at the top of the document
between ««« and »»» or between --- and ---). (since v.1.8.5)
`js
var conv = new showdown.Converter({metadata: true});
var html = conv.makeHtml(someMd);
var metadata = conv.getMetadata(); // returns an object with the document metadata
`
* splitAdjacentBlockquotes: (boolean) [default false] Split adjacent blockquote blocks.(since v.1.8.6)
NOTE: Please note that until version 1.6.0, all of these options are DISABLED by default in the cli tool.
javascript
showdown.setFlavor('github');
`
$3
`javascript
converter.setFlavor('github');
`
CLI Tool
Showdown also comes bundled with a Command Line Interface tool. You can check the [CLI wiki page][cli-wiki] for more info
Integration with AngularJS
ShowdownJS project also provides seamlessly integration with AngularJS via a "plugin".
Please visit https://github.com/showdownjs/ngShowdown for more information.
Integration with TypeScript
If you're using TypeScript you maybe want to use the types from [DefinitelyTyped][definitely-typed]
Integration with SystemJS/JSPM
Integration with SystemJS can be obtained via the third party "system-md" plugin.
Integration with VueJS
To use ShowdownJS as a Vue component quickly, you can check vue-showdown.
XSS vulnerability
Showdown doesn't sanitize the input. This is by design since markdown relies on it to allow certain features to be correctly parsed into HTML.
This, however, means XSS injection is quite possible.
Please refer to the wiki article [Markdown's XSS Vulnerability (and how to mitigate it)][xss-wiki]
for more information.
Extensions
Showdown allows additional functionality to be loaded via extensions. (you can find a list of known showdown extensions [here][ext-wiki])
You can also find a boilerplate, to create your own extensions in [this repository][boilerplate-repo]
$3
`js
var converter = new showdown.Converter({ extensions: ['twitter'] });
`
$3
`js
var showdown = require('devextreme-showdown'),
myExtension = require('myExtension'),
converter = new showdown.Converter({ extensions: ['myExtension'] });
`
Tests
A suite of tests is available which require node.js. Once node is installed, run the following command from
the project root to install the dependencies:
npm install
Once installed the tests can be run from the project root using:
npm test
New test cases can easily be added. Create a markdown file (ending in .md) which contains the markdown to test.
Create a .html file of the exact same name. It will automatically be tested when the tests are executed with mocha`.