[javascript] How to create a showdown.js markdown extension

Using the following code, I get working output:

<html>   <head>     <script type="text/javascript" src="/js/showdown.js"></script>   </head>   <body>     <script type="text/javascript">       var converter = new Showdown.converter();       alert(converter.makeHtml('*test* abc'));     </script>   </body> </html> 

Returning <p><em>test</em> abc</p>

I would now like to add an extension. The github page suggests this can be done with:

<script src="src/extensions/twitter.js" /> var converter = new Showdown.converter({ extensions: 'twitter' }); 

However, modifying my code to:

<html>   <head>     <script type="text/javascript" src="/js/showdown.js"></script>     <script type="text/javascript" src="/js/twitter.js"></script>   </head>   <body>     <script type="text/javascript">       var converter = new Showdown.converter({ extensions: 'twitter' });       alert(converter.makeHtml('*test* abc'));     </script>   </body> </html> 

Produces the error

"Uncaught Extension 'undefined' could not be loaded.  It was either not found or is not a valid extension." 

Adding the following code (as listed under the Filter example)

var demo = function(converter) {   return [     // Replace escaped @ symbols     { type: 'lang', function(text) {       return text.replace(/\\@/g, '@');     }}   ]; } 

Produces an error Uncaught SyntaxError: Unexpected token (

I would like to create an extension like this one https://github.com/rennat/python-markdown-oembed to interpret a ![video](youtube_link), but it's unclear how to begin adding this support.

This question is related to javascript showdown

The answer is

In your last block you have a comma after 'lang', followed immediately with a function. This is not valid json.


It appears that the readme was incorrect. I had to to pass an array with the string 'twitter'.

var converter = new Showdown.converter({extensions: ['twitter']}); converter.makeHtml('whatever @meandave2020'); // output "<p>whatever <a href="http://twitter.com/meandave2020">@meandave2020</a></p>" 

I submitted a pull request to update this.