JSFiddle - React, Tailwind, and code Playground

HTML

<span class="item">mark</span><span class="item show">jeff</span><span class="item" >arthur</span><span class="item show" >deniel</span>

CSS

.item{
    font-size:16px;
    color:#333;    
    display:none;
}

.item.show {
    display:inline;
}

.item.show:before{
    content:", ";
}
.item.show.first-of-type:before{
    content:"";
}

JavaScript

$('.item.show:first').addClass('first-of-type');