JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header">
  <h1>Startseite</h1>
  </div>
  <div id="container">
    <div id="left">
        Navigation
    </div>
    <div id="content"></div>
    <div id="right"></div>
    <div class="clr"></div>
  </div>

JavaScript

$( document ).ready(function() {
    var navdiv=$("#left").html();
    $("#left").html(navdiv+"fdsf");
});