Wrap elements and their previous and next siblings with vanilla javascript

wrap-elements-and-their-siblings-with-vanilla-javascript.js

// Get all the elements
document.querySelectorAll( '.my-element' ).forEach( (el) => {
  var prevEl = el.previousElementSibling, nextEl = el.nextElementSibling, elArr = [], html = '';
  if ( prevEl === null || nextEl === null ) return;

  // In case you want to include the two elements before the previous sibling
  [prevEl.previousElementSibling, prevEl.previousElementSibling.previousElementSibling].forEach((topEl) => {
    if ( topEl !== null ) elArr.push(topEl);
  })

  elArr.push(prevEl, el, nextEl);
  elArr.forEach( (elHTML) => html += elHTML.outerHTML );
  prevEl.insertAdjacentHTML( 'beforebegin','<div class="my-wrapper">' + html + '</div>' );
  elArr.forEach( (origin) => origin.remove() );
} );