JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://isotope.metafizzy.co/jquery.isotope.min.js"></script>
<div class="portfolio_projects = postit">
    <ul id='og-grid = yksipost'>
        <li>one</li>
        <li>two</li>
        <li>three</li>
    </ul>
</div>
<div class="portfolio_projects_hide = vanhatpostit">
    <ul>
        <li>four</li>
        <li>five</li>
        <li>six</li>
    </ul>
</div>

<a id='plus_projet' href="#">Add More</a>

CSS

ul {
    list-style: none;
}
ul li {
    display: inline-block;
    width: 230px;
    height: 180px;
    padding: 10px;
    border: 1px solid black;
    margin: 4px;
    background-color: #efefef;
}

.portfolio_projects_hide {
    display: none;
}

/**** Isotope Filtering ****/

.isotope-item {
  z-index: 2;
}

.isotope-hidden.isotope-item {
  pointer-events: none;
  z-index: 1;
}

/**** Isotope CSS3 transitions ****/

.isotope,
.isotope .isotope-item {
  -webkit-transition-duration: 0.8s;
     -moz-transition-duration: 0.8s;
      -ms-transition-duration: 0.8s;
       -o-transition-duration: 0.8s;
          transition-duration: 0.8s;
}

.isotope {
  -webkit-transition-property: height, width;
     -moz-transition-property: height, width;
      -ms-transition-property: height, width;
       -o-transition-property: height, width;
          transition-property: height, width;
}

.isotope .isotope-item {
  -webkit-transition-property: -webkit-transform, opacity;
     -moz-transition-property:    -moz-transform, opacity;
      -ms-transition-property:     -ms-transform, opacity;
       -o-transition-property:      -o-transform, opacity;
          transition-property:         transform, opacity;
}

/**** disabling Isotope CSS3 transitions ****/

.isotope.no-transition,
.isotope.no-transition .isotope-item,
.isotope .isotope-item.no-transition {
  -webkit-transition-duration: 0s;
     -moz-transition-duration: 0s;
      -ms-transition-duration: 0s;
       -o-transition-duration: 0s;
          transition-duration: 0s;
}

JavaScript

$('#yksipost').isotope({
    itemSelector: 'li'
});

$('#sort-by a').click(function () {
    var selector = $(this).attr('data-filter');
    $('#yksipost').isotope({
        filter: selector
    });
    $('#yksipost').isotope('reLayout');
    return false;
});

$('a#plus_projet').click(function () {
    var appendContent  = $('.vanhatpostit ul').html();
    var $appendContent = $(appendContent);
    
    $('.postit ul').append($appendContent).isotope('appended', $appendContent);
    
    // Not necessary when appending items...
    $('#yksipost').isotope('reLayout');
    return false;
});