Insert an HTML string after the end of the specified element

Use Element.insertAdjacentHTML() with a position of 'afterend' to parse htmlString and insert it after the end of el.

const insertAfter = (el, htmlString) =>
  el.insertAdjacentHTML('afterend', htmlString);

// Example
insertAfter(document.getElementById('myId'), '<p>after</p>');
// <div id="myId">...</div> <p>after</p>

Source

https://www.30secondsofcode.org/js/s/insert-after