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

ES6 syntax one liner:

function cloneAttributes(target, source) {
  [...source.attributes].forEach( attr => { target.setAttribute(attr.nodeName ,attr.nodeValue) })
}

And as noted in the first comment - you would probably don't want to copy the source id attribute... so this one will save it as a 'data-id' attribute in case you need a reference.

function cloneAttributes(target, source) {
  [...source.attributes].forEach( attr => { target.setAttribute(attr.nodeName === "id" ? 'data-id' : attr.nodeName ,attr.nodeValue) })
}

I'm facing same problem and after invested lots of time and effort i am creating thisclone textarea into editable div with same attribute

select.getAttributeNames().forEach(attrName => {
  $(div).attr(attrName, inputData.getAttribute(attrName));
});

A very straight to the point solution would be make something like this:

const _$ = domQuery => document.querySelector(domQuery)
let div1 = _$('#div-1')
let div2 = _$('#div-2')

for(attr of div1.attributes) {
  div2.setAttribute(attr.name, attr.value);
}

.my-div {
height: 100px;
width: 100px;
}

<h1>div-1</h1>
<div atribute-test="test" class="my-div" style="background: red" id="div-1"></div>
<h1>div-2</h1>
<div id="div-2"></div>

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)