Use a text field to filter Isotope items based on whatever is in their "data-category" attribute.

isotope.filter.js

$( function() {
  // quick search regex
  var qsRegex;
  
  // init Isotope
  var $grid = $('.grid').isotope({
    itemSelector: '.element-item',
    layoutMode: 'fitRows',
    filter: function() {
      return qsRegex ? $(this).data("category").match( qsRegex ) : true;
    }
  });

  // use value of search field to filter
  var $quicksearch = $('.quicksearch').keyup( debounce( function() {
    qsRegex = new RegExp( $quicksearch.val(), 'gi' );
    $grid.isotope();
  }, 200 ) );
  
});

// debounce so filtering doesn't happen every millisecond
function debounce( fn, threshold ) {
  var timeout;
  return function debounced() {
    if ( timeout ) {
      clearTimeout( timeout );
    }
    function delayed() {
      fn();
      timeout = null;
    }
    timeout = setTimeout( delayed, threshold || 100 );
  }
}