Each на jQuery,по какой-то причине меняет класс всех элементов игнорируя условия

$.each(response.data, function(index, value) {
  if (response.data[index].exists_status == 'exi') {
    item_class = 'result-item-regular';
    $('.result-item').attr('class', 'result-item result-item-regular').index();
  }
  if (response.data[index].exists_status == 'dex') {
    item_class = 'result-item-easy';
    $('.result-item').attr('class', 'result-item result-item-easy').index();
  } else {
    item_class = 'result-item-hard';
    $('.result-item').attr('class', 'result-item result-item-hard').index();
  }
})

<div class="result-item result-item-regular" data-domain="about.me" data-url="https://about.me/awd" data-instruction_text="null" data-instruction_add="" data-instruction_remove="" data-remove_difficulty="0">
  <p><a href="https://about.me/awd" target="_blank" class="exists">about.me</a></p><span style="margin: 5px 0px;" class="badge badge-light">поиск</span>
</div>
<div class="result-item result-item-regular" data-domain="angel.co" data-url="https://angel.co/company/awd" data-instruction_text="null" data-instruction_add="" data-instruction_remove="" data-remove_difficulty="0">
  <p><a href="https://www.angel.co" target="_blank" class="exists">angel.co</a></p><span style="margin: 5px 0px;" class="badge badge-light">поиск</span>
</div>
<div class="result-item result-item-regular" data-domain="ask.fm" data-url="https://ask.fm/awd" data-instruction_text="null" data-instruction_add="" data-instruction_remove="" data-remove_difficulty="0">
  <p><a href="https://ask.fm/awd" target="_blank" class="exists">ask.fm</a></p><span style="margin: 5px 0px;" class="badge badge-light">поиск</span>
</div>
<div class="result-item result-item-regular" data-domain="bandcamp.com" data-url="https://bandcamp.com/awd" data-instruction_text="null" data-instruction_add="" data-instruction_remove="" data-remove_difficulty="0">
  <p><a href="https://bandcamp.com/awd" target="_blank" class="exists">bandcamp.com</a></p><span style="margin: 5px 0px;" class="badge badge-light">поиск</span>
</div>
<div class="result-item result-item-regular" data-domain="befilo.com" data-url="https://befilo.com/profile/awd" data-instruction_text="null" data-instruction_add="" data-instruction_remove="" data-remove_difficulty="0">
  <p><a href="https://www.befilo.com" target="_blank" class="exists">befilo.com</a></p><span style="margin: 5px 0px;" class="badge badge-light">поиск</span>
</div>
<div class="result-item result-item-regular" data-domain="behance.net" data-url="https://www.behance.net/awd" data-instruction_text="null" data-instruction_add="" data-instruction_remove="" data-remove_difficulty="0">
  <p><a href="https://www.behance.net/awd" target="_blank" class="exists">behance.net</a></p><span style="margin: 5px 0px;" class="badge badge-light">поиск</span>
</div>
<div class="result-item result-item-regular" data-domain="blogspot.com" data-url="https://awd.blogspot.com/" data-instruction_text="null" data-instruction_add="" data-instruction_remove="" data-remove_difficulty="0">
  <p><a href="https://awd.blogspot.com/" target="_blank" class="exists">blogspot.com</a></p><span style="margin: 5px 0px;" class="badge badge-light">поиск</span>
</div>