将CSS类从一个页面设置为另一个页面 - WordPress，jQuery AJAX

Question

In WP theme I have post.php (for single post item) and blog.php (for blog layout). On single post, CSS classes are added to post div via jQuery (on click).

How to get that classes (strings)from single post (post.php) and use them in blog.php?

EG. Single post (post.php) print this html

<article class="single-post post-1">
<p>sometext</p>
<a>click</a>
</article>
<script>
jQuery("a").click(function(){
   jQuery("article").addClass("singleClass");
});
</script>

Blog posts (blog.php)

<article class="blog-post post-1">
<p>sometext</p>
</article>
<article class="blog-post post-2">
<p>sometext</p>
</article>

And also to get class from single post 1 and add it to blog post 1, post 2 to post 2, etc. First time trying AJAX, so I'm not sure what to do. jQuery in post.php

var postClass = voteText+'-'+voteNumber; //some variables declared earlier
jQuery.ajax({
    type: "POST",
    url: "ajax-class.php", //or /wp-admin/admin-ajax.php? This mean that data is posted to this file?
    data: { 'dataString': postClass },
    cache: false,
    success: function() {
        alert("Classes: "+postClass); // alert goes fine
    }
});

now I need to GET data from ajax-class.php?

<?php  echo 'Classes: '. $_POST['postClass']; ?>

This is not working. If someone could just point me to right direction. Documentation and stuff. Thanx