<form id="tableForm" action="getJson">
        <select class="example" name="example">
              <option name="table1" value="1">Table 1</option>
              <option name="table2" value="2">Table 2</option>
              <option name="table3" value="3">Table 3</option>
        </select>
    </form>

你应该寻找在selected标签<option>属性。此外属性attribute不支持<option>标签。你不能从<select>标签的索引。您应该创建与此<select>索引和值的哈希表。然后当你将获得价值得到从哈希表中该值的索引。类似的东西。只是举例。

<form id="tableForm" action="getJson">
    <select class="example" name="example">
          <option value="Berlin">Berlin</option>
          <option value="Moscow">Moscow</option>
          <option value="Kyiv">Kyiv</option>
    </select>
</form>

const selectHashtable = {
    'Berlin': 1,
    'Moscow': 2,
    'Kyiv': 3
};

// for example req.body.example = 'Kyiv';
// you call 
selectHashtable[req.body.example]; // console.log => 3

获取选定的选项在node.js的索引使用快递

我需要使用快递在app.js example.html的安慰它得到所选对象的索引

<form id="tableForm" action="getJson">
        <select class="example" name="example">
              <option name="table1" value="1">Table 1</option>
              <option name="table2" value="2">Table 2</option>
              <option name="table3" value="3">Table 3</option>
        </select>
    </form>

<form id="tableForm" action="getJson">
    <select class="example" name="example">
          <option value="Berlin">Berlin</option>
          <option value="Moscow">Moscow</option>
          <option value="Kyiv">Kyiv</option>
    </select>
</form>

const selectHashtable = {
    'Berlin': 1,
    'Moscow': 2,
    'Kyiv': 3
};

// for example req.body.example = 'Kyiv';
// you call 
selectHashtable[req.body.example]; // console.log => 3