Выпадающее меню на JS

function dropdown() {
        const selectItem = document.querySelectorAll(".select__output");

        selectItem.forEach((item, i) => {
            item.addEventListener("focusin", (event) => {
                const selectBody = document.querySelectorAll(".select__body");

                selectBody[i].classList.toggle("show");
                item.classList.toggle("shadow");
            });
            item.addEventListener("focusout", (event) => {
                const selectBody = document.querySelectorAll(".select__body");

                selectBody[i].classList.toggle("show");
                item.classList.toggle("shadow");
            });
        });
    }
    
    
    dropdown();

.select {
  width: 60%;
}

.select:not(:last-child) {
  margin-right: 32px;
}

.selects__title {
  font-weight: normal;
  font-size: 18px;
  line-height: 25px;
  letter-spacing: 0.02em;
  color: #111111;
  opacity: 0.8;
  margin-bottom: 16px;
  margin-left: 16px;
}

.select__item {
  position: relative;
}

.select__output {
  display: flex;
  justify-content: space-between;
  width: 100%;
  height: 36px;
  padding: 15px 16px;
  background: #FFFFFF;
  border: 2px solid rgba(125, 138, 253, 0.3);
  border-radius: 4px;
  cursor: pointer;
}

.shadow {
  box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.2);
}

.select__content {
  font-weight: normal;
  font-size: 18px;
  line-height: 25px;
  letter-spacing: 0.02em;
  color: #777;
  opacity: 0.8;
}

.select__body {
  position: absolute;
  top: 64px;
  left: 0;
  width: 100%;
  max-height: 379px;
  padding: 24px 16px;
  background: #FFFFFF;
  border: 2px solid rgba(125, 138, 253, 0.3);
  box-shadow: 0 0 20px rgba(0, 0, 0, 0.04);
  border-radius: 4px;
  overflow-y: scroll;
  z-index: 1;
}

.select-body__height {
  height: 443px;
}

.select-body__list {
  list-style: none;
}

.select-body__item:not(:last-child) {
  margin-bottom: 16px;
}

.select-body__item:last-child {
  margin-bottom: 20px;
}

.select__btn {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
}

.select-btn__item {
  background: #638FFF;
  border-radius: 4px;
  padding: 9px 63px;
  border: none;
  margin: 0 auto;
  font-weight: bold;
  line-height: 22px;
  text-align: center;
  color: #FFFFFF;
}

.hide {
  display: none;
}

.show {
  display: block;
}

<div class="select">
  <p class="selects__title">Отрасль</p>
  <div class="select__item">
    <div class="select__output" tabindex="1">
      <div class="select__content">Выбрать</div>
      <img src="img/arrowSelect.svg" alt="arrow" class="select__arrow">
    </div>
    <div class="select__body hide">
      <ul class="select-body__list">
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox01">
          <label for="checkbox01" class="label__checkbox">Дизайн</label>
        </li>
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox02">
          <label for="checkbox02" class="label__checkbox">Дизайн</label>
        </li>
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox03">
          <label for="checkbox03" class="label__checkbox">Дизайн</label>
        </li>
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox04">
          <label for="checkbox04" class="label__checkbox">Дизайн</label>
        </li>
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox05">
          <label for="checkbox05" class="label__checkbox">Дизайн</label>
        </li>
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox06">
          <label for="checkbox06" class="label__checkbox">Дизайн</label>
        </li>
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox07">
          <label for="checkbox07" class="label__checkbox">Дизайн</label>
        </li>
        <li class="select-body__item">
          <input type="checkbox" class="checkbox" id="checkbox08">
          <label for="checkbox08" class="label__checkbox">Дизайн</label>
        </li>
      </ul>
      <div class="select__btn">
        <input type="submit" value="Применить" class="select-btn__item">
      </div>
    </div>
  </div>
</div>