在div而不是input/textarea中时，无法通过POST发送内容

<div>
  <input type="hidden" id="contentInput">
  <button onclick="submitForm()">提交</button>
</div>

<script>
  function submitForm() {
    var content = "需要发送的内容";
    document.getElementById("contentInput").value = content;
    document.getElementById("myForm").submit();
  }
</script>

<div>
  <button onclick="sendData()">提交</button>
</div>

<script>
  function sendData() {
    var content = "需要发送的内容";
    var xhr = new XMLHttpRequest();
    xhr.open("POST", "服务器URL", true);
    xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    xhr.onreadystatechange = function() {
      if (xhr.readyState === 4 && xhr.status === 200) {
        // 请求成功的处理逻辑
      }
    };
    xhr.send("content=" + encodeURIComponent(content));
  }
</script>