Using the following code, I get working output:
In your last block you have a comma after 'lang', followed immediately with a function. This is not valid json.
EDIT
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.
The way we write extensions has changed, I found some help with the following filter example : http://codepen.io/tivie/pen/eNqOzP
showdown.extension("example", function() {
'use strict';
return [
{
type: 'lang',
filter: function(text, converter, options) {
var mainRegex = new RegExp("(^[ \t]*:>[ \t]?.+\n(.+\n)*\n*)+", "gm");
text = text.replace(mainRegex, function(match, content) {
content = content.replace(/^([ \t]*):>([ \t])?/gm, "");
var foo = converter.makeHtml(content);
return '\n<blockquote class="foo">' + foo + '</blockquote>\n';
});
return text;
}
}
]
});