从选择列表中获取选择值，并将其连接到表单中的Post操作

<select id="mySelect">
  <option value="option1">Option 1</option>
  <option value="option2">Option 2</option>
  <option value="option3">Option 3</option>
</select>

var selectElement = document.getElementById("mySelect");
var selectedValue = selectElement.value;

var formElement = document.getElementById("myForm");
var inputElement = document.createElement("input");
inputElement.type = "hidden";
inputElement.name = "selectedOption";
inputElement.value = selectedValue;
formElement.appendChild(inputElement);
formElement.submit();