JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper"><div class="content-block">Content</div></div>
<div class="wrapper"><div class="content-block">Content</div></div>
<div class="wrapper"><div class="content-block">Content</div></div>
<div class="wrapper"><div class="content-block">Content</div></div>
<div class="wrapper"><div class="content-block">Content</div></div>

JavaScript

$("document").ready(function () {;
        $.each($(".wrapper > .content-block"), function(index, value){
            var num = index + 1;
            $(value).attr("id","post"+ num);
        });
    });