JSFiddle - React, Tailwind, and code Playground

HTML

<div class="autocomplite_input">
            <div contentEditable=true data-text="Выберите регион" class="modal-open" id="modalmd"></div>
            <div class="modal" id="modal1">
              <div class="dialog">
                <div class="header_content_modal">
                  <p class="header_modal">Выберите регион заявок</p>
                  <div class="close_btn" id="close_cont">
                    <i class="fas fa-times"></i>
                  </div>
                </div>
                <ul class="content_item">
                  <li class="selected headmd">
                    <div class="text_item" data-filter="all" id="namecity">Любой регион</div>
                  </li>
                  <li class="selected">
                    <div class="text_item" data-filter="Altajskij" id="namecity">Алтайский край</div>
                  </li>
                  <li class="selected">
                    <div class="text_item" data-filter="Belgorodskaja" id="namecity">Белгородская область</div>
                  </li>
                  <li class="selected">
                    <div class="text_item" data-filter="Brjanskaja">Брянская область</div>
                  </li>
                  <li class="selected">
                    <div class="text_item" data-filter="Vladimirskaja">Владимирская область</div>
                  </li>
                  <li class="selected">
                    <div class="text_item" data-filter="Volgogradskaja">Волгоградская область</div>
                  </li>
                  <li class="selected">
                    <div class="text_item" data-filter="Vologodskaja">Вологодская область</div>
                  </li>
                  </li>
                </ul>
              </div>
            </div>
          </div>

JavaScript

var a = document.querySelectorAll(".text_item");

    [].forEach.call(a, function (el) {
      el.onclick = function () {
        var text_item = this.textContent;
        document.querySelector(".modal-open").innerText = text_item;

      };
    });