JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
<div class="selector">
    test
</div>
<div class="selector">
    test
</div>
<div class="selector">
    test
</div>
<div class="selector">
    test
</div>
<div class="selector">
    test
    </div></div>
<input type="button" value="ADD"/>

CSS

.wrap{
     width:500px;  
}
.activator{
    color:blue;
}

JavaScript

var elms = $('.selector', '.container');
$('input:button').click(function(){
    $('.container').append('<div class="selector">test');
});
$('.container').on('click', '.selector', function(event, ui) {
        event.preventDefault();
        var elm = $(this);
        alert(elm.index());
});