JSFiddle - React, Tailwind, and code Playground

HTML

<div id="myDiv">aaaaaaaaaaaaaaaaaaaaaaaaa</div>

JavaScript

$(function() {
    var html=$('#myDiv').html();
    var newHtml='';
    for (var i=0;i<html.length;i++) {
        newHtml=newHtml+html[i];
        if ((i+1)%10==0) {newHtml=newHtml+'<br/>';}
    }
    $('#myDiv').html(newHtml);
});