SO-34050904

by David Thomas

HTML

<script src="//ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<img src="whatever.jpg" />
<span>Copyright Stackoverflow</span>

CSS

span {
  color: limegreen;
}

figcaption {
  color: #f90;
}

JavaScript

function replaceWith(original, tag) {
  tag = tag.replace(/<|>/g, '');
  var newEl = document.createElement(tag);
  newEl.innerHTML = original.innerHTML;

  original.parentNode.replaceChild(newEl, original);
}

var elements = document.querySelectorAll('img + span'),
  elementArray = Array.prototype.slice.call(elements, 0);

elementArray.forEach(function (elem) {
  replaceWith(elem, '<figcaption>')
});