Replace an element with a new one that has a different tagName

changeTag.js

export default function changeTag(original, tagName){
  // Create a replacement tag of the desired type
  const replacement = document.createElement(tagName)
  
  // Grab all of the original's attributes, and pass them to the replacement
  Array.prototype.forEach.call(original.attributes, ({name, value}) => {
    replacement.setAttribute(name, value)
  })
  
  // Persist contents
  replacement.append(...original.childNodes)
  
  // Switch!
  original.replaceWith(replacement)
  
  return replacement
}