Registration of extensions changed

[jwt625]

See Showdown CHANGELOG for detail.
So I just modified the third last line in showdown-toc.js from
if (typeof window !== 'undefined' && window.showdown && window.showdown.extensions) { window.showdown.extensions.toc = toc; }
to
if (typeof window !== 'undefined' && window.showdown && window.showdown.extension) { window.showdown.extension("showdown-toc",toc); }
and initialize the converter with option { extensions: ['showdown-toc'] }, it works.
Hope this can help.

[jwt625]

Here for the corrected version (which also fixed interruption from lower level toc).

[byYufeng]

Here for the corrected version (which also fixed interruption from lower level toc).

I catch error after using your code:
Uncaught Error: Extension "showdowntoc" could not be loaded.

[ahungrynoob]

I create a new one, https://github.com/ahungrynoob/showdown-toc