phpjs/_octopress/.themes/classic/source/_includes/post/author.html

php.js offers community built php functions in javascript

{% if post.author %}
  {% assign author = post.author %}
{% elsif page.author %}
  {% assign author = page.author %}
{% else %}
  {% assign author = site.author %}
{% endif %}
{% if author %}<span class="byline author vcard">Posted by <span class="fn">{{ author }}</span></span>{% endif %}