Show related posts on tumblr permalink pages.
Prerequisites: jQuery.

Usage

<script>
    $(container).relatedposts(options);
</script>

container should be a valid jQuery selector. options should be an object with key/value pairs.

Possible options

domain: Your tumblr domain name e.g. mytumblr.tumblr.com. Defaults to current document domain.
num: Max. number of related posts to display.
len: Excerpt text length (number of characters).
thumbwidth: Preferred thumbnail width in px (height will scale accordingly).
tags: Array of post tags to search for.
type: Limit posts to type. Empty string (“) for all types.
titlehtml: HTML for the title tag (will be inserted before the container).

The only required option is the tags option, which should be an array of post tags.

Minimal example

Assuming you have a container with ID related in which you want to display, insert this just before the closing </body> of your theme (change your domain/path accordingly, and leave jQuery out if it is already included on the page):

{block:PermalinkPage}
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js">
    </script>
    {block:Posts}
        {block:HasTags}
            <script src="//yourdomain.com/js/related.js"></script>
            <script>
                $('#related').relatedposts(
                    {tags: [{block:Tags}'{Tag}',{/block:Tags}]});
            </script>
        {/block:HasTags}
    {/block:Posts}
{/block:PermalinkPage}

You could also pull the tags via jQuery (in the example assuming post tags are displayed as links in a container with the class tags):

{block:PermalinkPage}
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js">
    </script>
    {block:Posts}
        {block:HasTags}
            <script src="//yourdomain.com/js/related.js"></script>
            <script>
                $('#related').relatedposts(
                    {tags: $('.tags a').map(function() {
                               return $(this).text().replace(/^#/, '');
                           }).get()});
            </script>
        {/block:HasTags}
    {/block:Posts}
{/block:PermalinkPage}

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