Can’t filter categories using isotope

I’m trying to initialise isotope https://isotope.metafizzy.co/ in WordPress so I can start filtering posts based on their categories. I think I’m missing some php in the <a href='#' data-filter='.".$term->slug."'>" . $term->name . "</a> section because when i click on the category it gives me a /# instead of filtering the categories. I’m really trying to achieve this filtering effect: https://nmbw.com.au/works-and-projects/

I’m new to this so any help would be really appreciated.

Here’s what I have:

<?php
/**
 * Template Name: isotope
 *
 * Template for displaying a page without sidebar even if a sidebar widget is published.
 *
 * @package understrap
 */

get_header();
$container = get_theme_mod( 'understrap_container_type' );
?>

<ul id="filters">
    <li><a href="#" data-filter="*">All categories</a></li>
<?php
$terms = get_terms("category"); // get all categories, but you can use any taxonomy
$count = count($terms); //How many are they?
if ( $count > 0 ){  //If there are more than 0 terms
foreach ( $terms as $term ) {  //for each term:
echo "<li><a href='#' data-filter='.".$term->slug."'>" . $term->name . "</a></li>n";
//create a list item with the current term slug for sorting, and name for label
}
}
?>
</ul>


<?php $the_query = new WP_Query( 'posts_per_page=9' ); //Check the WP_Query docs to see how you can limit which posts to display ?>
<?php if ( $the_query->have_posts() ) : ?>
    <div id="isotope-list">
    <?php while ( $the_query->have_posts() ) : $the_query->the_post();
$termsArray = get_the_terms( $post->ID, "category" );  //Get the terms for this particular item
$termsString = ""; //initialize the string that will contain the terms
foreach ( $termsArray as $term ) { // for each term
$termsString .= $term->slug.' '; //create a string that has all the slugs
}
?>
<div class="<?php echo $termsString; ?> item">
<h3><?php the_title(); ?></h3>
        <?php if ( has_post_thumbnail() ) {
                      the_post_thumbnail();
                } ?>
</div> <!-- end item -->
    <?php endwhile;  ?>
    </div> <!-- end isotope-list -->
<?php endif; ?>
<?php get_footer(); ?>

This is what I have in my functions.php file

function add_isotope() {
wp_register_script( 'isotope', get_template_directory_uri().'/js/libs/isotope.pkgd.min.js', array('jquery'),  true );
wp_register_script( 'isotope-init', get_template_directory_uri().'/js/isotope.js', array('jquery', 'isotope'),  true );
wp_register_script( 'isotope-custom', get_template_directory_uri().'/js/isotope-custom.js', array('jquery', 'isotope'),  true );
wp_register_style( 'isotope-css', get_stylesheet_directory_uri() . '/css/isotope.css' );

wp_enqueue_script('isotope-init');
wp_enqueue_style('isotope-css');
}

add_action( 'wp_enqueue_scripts', 'add_isotope' );  

This is in my isotope-custom.js file

jQuery(function ($) {

var $container = $('#isotope-list'); //The ID for the list with all the 
blog posts
$container.isotope({ //Isotope options, 'item' matches the class in the 
PHP
itemSelector : '.item', 
layoutMode : 'masonry'
});

//Add the class selected to the item that is clicked, and remove from 
the others
var $optionSets = $('#filters'),
$optionLinks = $optionSets.find('a');

$optionLinks.click(function(){
var $this = $(this);
// don't proceed if already selected
if ( $this.hasClass('selected') ) {
return false;
}
var $optionSet = $this.parents('#filters');
$optionSets.find('.selected').removeClass('selected');
$this.addClass('selected');

//When an item is clicked, sort the items.
var selector = $(this).attr('data-filter');
$container.isotope({ filter: selector });

return false;
});

});

This is in the isotope.js file
`jQuery(function ($) {

 //set the container that isotope will be inside of in a var

 var container = document.querySelector('#isotope-list');

 //create empty var isotope

 var Isotope;

 // initialize Isotope after all images have loaded
 var $container = $('#isotope-list').imagesLoaded( function() {
 $container.isotope({
 // options
 });
 });




 var $container = $('#isotope-list'); //The ID for the list with all 
 the blog posts
 $container.isotope({ //Isotope options, 'item' matches the class in 
 the PHP
 itemSelector : '.item',
 layoutMode : 'masonry',
 isOriginLeft: false
 });
 var container = document.querySelector('#isotope-list');
 // init
 var iso = new Isotope( container, {
 // options
 itemSelector: '.item',

 });

 //Add the class selected to the item that is clicked, and remove from 
 the others
 var $optionSets = $('#filters'),
 $optionLinks = $optionSets.find('a');

  $optionLinks.click(function(){
  var $this = $(this);
  // don't proceed if already selected
  if ( $this.hasClass('selected') ) {
  return false;
  }
  var $optionSet = $this.parents('#filters');
  $optionSets.find('.selected').removeClass('selected');
  $this.addClass('selected');

  //When an item is clicked, sort the items.
  var selector = $(this).attr('data-filter');
  $container.isotope({ filter: selector });

  return false;
  });

  });

  jQuery( function($) {

  $('.isotope').isotope({
  itemSelector: '.item',
  masonry: {
  columnWidth: 100
  }
  });

  });`