迭代数组的第一个元素

$(".room-guests-count").click(function(e){
	$(".form-open").toggle();
	e.stopPropagation();
});
$('.form-open').click(function(e) {
  e.stopPropagation();
});
$(document).click(function() {
  $('.form-open').hide();
});

const room = document.querySelector('.room-guests-count');
const form = document.querySelector('.form-open');
const adultsChildren = document.querySelector('.adults-children');
const adultsChildrenWrapper = document.querySelector('.adults-children-wrapper');

// let roomCount = document.querySelectorAll("room-count");
let roomCount = document.querySelectorAll(".room-count");

   
// roomCount.style.backgroundColor = "red";

let formIsOpened = false;

room.onclick = () => {
  if(!formIsOpened) {
    form.style.display = 'block'
  } else {
    form.style.display = 'none'
  }
  formIsOpened = !formIsOpened;
}
const toggleRoom = () => {
  const addRoomButton = document.querySelector('#add-room');
  const removeRoomButton = document.querySelector('#remove-room');
  const countRoom = document.querySelector('.form-text');
  
  const addSection = () => {
    const wrapper = document.createElement("div"); //Создает новый элемент с указанным тегом:
    wrapper.className = "adults-children-wrapper"; // имя класса добавить к елементу
    // const template = adultsChildrenWrapper.innerHTML; // значение  adultsChildrenWrapper присваивается к template
    wrapper.innerHTML = adultsChildrenWrapper.innerHTML; // значение  adultsChildrenWrapper присваивается к wrapper                
    
      adultsChildren.appendChild(wrapper).querySelector(".room-count").innerText = countRoom.value;
      
  }
  const removeSection = () => {
    adultsChildren.lastChild.remove();
  }
  
  addRoomButton.onclick = () => {
    if(countRoom.value == 4) return;
    countRoom.value++;

    

    // roomCount.textContent++;
    // if (countRoom.value >= 2)
    addSection();
    
  }

  removeRoomButton.onclick = () => {
    if(countRoom.value == 1) return;
    countRoom.value--;
   
    
    removeSection();
  }
  
  
}
toggleRoom();

* {
  background:lightblue;
}
/*ROOM GUESTS COUNT*/
.room-guests-count {
	width: 17.2%;
	cursor: pointer;
	margin-right: 4%;
	background: #fff;
	float: right;
	height: 66px;
	margin-right: 149px;
}
.form-open {
	display: none;
	position: absolute;
	z-index: -1;
	top: 110px;
	background-color: #fff;
	height: auto;
	right: -8px;
	width: 348px;
}

.form-open:after {
	content: '';
	position: absolute;
	width: 0;
	height: 0;
	border-bottom: 10px solid #fff;
	border-left: 10px solid transparent;
	border-right: 10px solid transparent;
	right: 300px;
	top: -10px;
}
.room-guests-content {
	padding-top: 23px;
	padding-left: 15px;
}
.click_hidden_text {
	position: absolute;
	z-index: 1;
	left: 163px;
	top: 56px;
	opacity: 0.8;
}
.form-search {
	padding: 0;
	margin: 10px 10px 5px 10px;
	
}
.form-item {
	padding: 10px 5px;
	clear: both;
	height: 14px;
}
.edit-rooms {
	font-weight: normal;
	font-size: 13px;
	float: left;
	color: #000;
	margin-right: 5px;
}
.rooms-guests-plus {
	float: right;
	color: #fff;
	background:#ccc;
	width: 24px;
	height: 24px;
	text-align: center;
	line-height: 24px;
	top: -6px;
	position: relative;
	font-size: 18px;
	cursor: pointer;
}
.form-text {
	text-align: center;
	width: 6%;
	width: 20px !important;
	text-decoration: center;
	float: right;
	border:0;
	padding: 0;
	height: auto;
	outline: 0;
	vertical-align: middle;
}
.textfield label {
	margin-right: 2.5px;
	display: inline;
	font-size: 13px;
}
.children-1 label {
	display: inline;
	font-size: 13px;
}
.rooms-guests-minus {
	float: right;
	color: #fff;
	background:#e7e7e7;
	width: 24px;
	height: 24px;
	text-align: center;
	line-height: 24px;
	top: -6px;
	position: relative;
	font-size: 18px;
	cursor:auto;
}
.adults-children {
	clear: both;
}
.rooms-id {
	line-height: 40px;
	float: left;
	padding:5px 0 0 15px;
	color: #000;
}
.already-min {
	float: right;
	margin: -16px 0px 2px 6px;
	padding: 0;
	background: #fff;
}
.already-min-search {
	float: right;
	margin: 5px 10px 5px 2px;
}
.adults-children-wrapper {
	clear: both;
}
.children-1 {
	padding: 10px 5px;
	clear: both;
	height: 14px;
}
.edit-children {
	font-weight: normal;
	font-size: 13px;
	float: left;
	color: #000;
	margin-right: 5px;
}
.textfield {
	clear: both;
	height: 14px;
	margin: 0;
	position: relative;
	margin-top: 32px;
}
/*FORM FINISHED*/

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="room-guests-count">
  <div class="room-guests-content">
    Взрослых
    <span class="ga-count">2</span>
    , Детей 
    <span class="children-count">0</span>
  </div>
</div>
<div class="form-open">
  <div class="form-search">
    <div class="form-item">
      <label class="edit-rooms">Количество номеров</label>
      <div class="rooms-guests-plus" id="add-room">+</div>
      <input type="text" name="rooms" max="9" min="1" maxlength="128" class="form-text" value="1" size="60" readonly="readonly">
      <div class="rooms-guests-minus" id="remove-room">-</div>
    </div>
  </div>
  <div class="adults-children">
    <div class="adults-children-wrapper">
      <div class="rooms-id">Номер <span class="room-count">1</span>:</div>
      <div class="already-min-search">
        <div class="children-1">
          <label for="edit-children">Детей</label>
          <div class="rooms-guests-plus">+</div>
          <input type="text" name="childrenqt" value="0" max="5" min="0" maxlength="5" size="60" maxlength="128" class="form-text">
          <div class="rooms-guests-minus">-</div>
        </div>
      </div>
      <div class="already-min">
        <div class="textfield">
          <label for="edit">Взрослых</label>
          <div class="rooms-guests-plus">+</div>
          <input type="text" name="edit" value="2" max="10" min="0" maxlength="5" size="60" maxlength="128" class="form-text">
          <div class="rooms-guests-minus">-</div>
        </div>
      </div>
    </div>
  </div>
</div>