Wordpress Categories in data-groups

Question

I'm building a jQuery masonry type gallery in Wordpress, which works off categories. I'm 90% there but need to display the categories in a data-groups tag for it to work. ie:

<div class="project" data-groups='["category1","category2",category3"]'>

I'm using to following function:

function the_category_unlinked($separator = ' ') {
    $categories = (array) get_the_category();

    $thelist = '';
    foreach($categories as $category) {
       $thelist .= """ . $category->category_nicename . "",";
    }

    echo $thelist;
}

with:

<div class="project" data-groups='<?php the_category_unlinked(' '); ?>'>

which works, but this echos out the categories with a comma at the end and breaks the entire working effect:

<div class="project" data-groups='["category1","category2",category3",]'>

What can I do to display these categories as needed? It could also be done using tags if that would work...

Answer 1

Just remove the trailing comma with some good ole php before echoing it out.

$thelist = rtrim($thelist, ',');