JSFiddle - React, Tailwind, and code Playground

HTML

<div class='panel'>
    <div id="wrapper">
        <div id='m' class='new'>
            
        </div>
    
        <div class="w">
        </div>   
    </div>
</div> 

<input type="button" value="del" id="btnDel">
<input type="button" value="add" id="btnAdd">

SCSS

.panel {    
  width: 400px; 
  height: 100px;   
  border: 1px solid blue; 
  background-color: blue;
}

#wrapper {    
   border: 2px solid blue;
   height: 120px; 
   overflow: hidden; 
}
#wrapper:after {
    display: block;
    clear: both;
    content: '';
}
  
.w {
   margin-top: 1px;
   margin-bottom: 8px;
   padding: 5px;
   float: none;
   overflow: hidden;
   background-color: cadetblue;
}

.new {
   border: 2px solid fuchsia;
   overflow: hidden;
   float: left;
}

JavaScript

$('#btnDel').click(function(){
    var elem = $('.kv');
    //console.log(elem.length);
    elem[elem.length - 1].remove();
}); 

$('#btnAdd').click(function(){
    var elem = $('#m'),
       imgKv = '<img src="http://images.gizmag.com/gallery_tn/cassini-earth-image-1.jpg" class="item kv"/>';
    //console.log(elem.length);
    elem.append(imgKv);
});