JSFiddle - React, Tailwind, and code Playground

HTML

<h1 id="ovde">
  ...
</h1>

JavaScript

let customItems = "1,2,3";
      customItems = customItems.split(',');
      
      for ( let i = 0; i < customItems.length; i++ )
        customItems[i] = "- " + customItems[i] + "<br>";
      
      customItems = customItems.join('');
      
      document.getElementById("ovde").innerHTML = customItems;