<section id='first'>
 ...
</section>
<section id='first'>
 ...
</section>

<script>
  const firstSection = document.querySelector('#first')
  const secondSection = document.querySelector('#second')
  
  for (let element of firstSection.querySelectorAll('[data-feather]')) {
    feather.replaceElement(element, { class: 'foo bar', 'stroke-width': 1 })
  }
  
  for (let element of secondSection.querySelectorAll('[data-feather]')) {
    feather.replaceElement(element)
  }
</script>