How to copy all the attributes of one element and apply them to another?

Answer 1

Javascript solution

Copy the attributes of old element to the new element

const $oldElem = document.querySelector('.old')
const $newElem = document.createElement('div')

Array.from($oldElem.attributes).map(a => {
  $newElem.setAttribute(a.name, a.value)
})

Replace the old element with the new element, if required

$oldElem.parentNode.replaceChild($newElem, $oldElem)