title: Input value is not changed on Javascript
body: <p>I make shopping Cart now with vanilla javascript, html, css.</p>
  <p>This program is when consumer click selection tag, add new tag and change count.</p>
  <p>To Add new Tag is already working. Change count is not work. When I clicked, selectA, selectB, selectC is changed but not working on input tag.</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var selectA = 0;
  var selectB = 0;
  var selectC = 0;
  
  function handleOnChange(e) {
    // 선택된 데이터 가져오기
    let value = e.value;
    let name = e.options[e.selectedIndex].text;
    let itemList = document.getElementById("addItem");
  
    var Item = document.createElement('div');
    var itemName = document.createElement('div');
    var itemSumA = document.createElement('input');
    var itemSumB = document.createElement('input');
    var itemSumC = document.createElement('input');
    itemName.innerHTML = name;
  
    if (value === "A") {
      if (selectA === 0) {
        Item.appendChild(itemName);
        Item.appendChild(itemSumA);
        itemList.appendChild(Item);
      }
      itemSumA.value = selectA;
    } else if (value === "B") {
      console.log(selectB);
      if (selectB === 0) {
        Item.appendChild(itemName);
        Item.appendChild(itemSumB);
        itemList.appendChild(Item);
      }
      itemSumB.value = ++selectB;
    } else {
      if (selectC === 0) {
        Item.appendChild(itemName);
        Item.appendChild(itemSumC);
        itemList.appendChild(Item);
      }
      itemSumC.value = ++selectC;
    }
  
    document.getElementById("Sum").innerHTML = selectA * 39800 + selectB * 49800 + selectC * 59800;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;li class="checked"&gt;
    &lt;button class="accordion"&gt;주문 정보&lt;/button&gt;
    &lt;div class="panel"&gt;
      &lt;p&gt;상품 선택&lt;/p&gt;
      &lt;select name="tent" id="tent" onchange="handleOnChange(this)"&gt;
        &lt;option value="A"&gt;A. 스피드 원터치 팝업텐트(3~4인용)&lt;/option&gt;
        &lt;option value="B"&gt;B. 5초 원터치 텐트(3인용) (+10,000)&lt;/option&gt;
        &lt;option value="C"&gt;C. 5초 원터치 텐트(5인용) (+20,000)&lt;/option&gt;
      &lt;/select&gt;
      &lt;div id="addItem"&gt;&lt;/div&gt;
  
    &lt;/div&gt;
  &lt;/li&gt;</code></pre>
  </div>
  </div>
  </p>
  <p>I want to know why.</p>