如何在另一个选择列表的更改函数上更改一个选择列表的值？[副本]

Question

我有这个select，它绑定了一个变更事件。在其内部值的change中，我想在另一个选择列表中选择一个特定的元素，即其中的一个特定选项。

然而它并不起作用。在主服务中有一些服务，如果选择了子服务，就不需要子服务，因此应该选择默认的-select-。

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$("#MainServices").change(function() {
  $(#SubServices).val("-Select-")
}

<select class="d-flex flex-wrap" name="MainServiceName" id="MainServices">
  <option selected value="m-None">-Select-</option>
  <option value="m-SS">Software Services</option>
  <option value="m-AIMS">Asset Integrity Management Services</option>
  <option value="m-HSE">HSE & Environmental Services</option>
  <option value="m-ES">Engineering Services</option>
</select>

<select class="d-flex flex-wrap" name="SubServiceName" id="SubServices">
  <option class="" selected value="s-None">-Select-</option>
  <option class="SoftwareServices" value="s-AIMS">VAIL-Plant (Asset Integrity Management System)</option>
  <option class="SoftwareServices" value="s-PHA">VAIL-PHA (Process Hazard Analysis)</option>
  <option class="SoftwareServices" value="s-PSRA">VAIL-PSRA (Petrol Station Risk Assessment)</option>
  <option class="SoftwareServices" value="s-MTS">VAIL-MTS (Material Tracking System)</option>
</select>

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Answer 1

-select-是该选项的文本，其值为s-none，因此应为

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$("#MainServices").change(function() {
  $("#SubServices").val("s-None")
});

html lang-html prettyprint-override"><script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select class="d-flex flex-wrap" name="MainServiceName" id="MainServices">
  <option selected value="m-None">-Select-</option>
  <option value="m-SS">Software Services</option>
  <option value="m-AIMS">Asset Integrity Management Services</option>
  <option value="m-HSE">HSE & Environmental Services</option>
  <option value="m-ES">Engineering Services</option>
</select>

<select class="d-flex flex-wrap" name="SubServiceName" id="SubServices">

  <option class="" selected value="s-None">-Select-</option>
  <option class="SoftwareServices" value="s-AIMS">VAIL-Plant (Asset Integrity Management System)</option>
  <option class="SoftwareServices" value="s-PHA">VAIL-PHA (Process Hazard Analysis)</option>
  <option class="SoftwareServices" value="s-PSRA">VAIL-PSRA (Petrol Station Risk Assessment)</option>
  <option class="SoftwareServices" value="s-MTS">VAIL-MTS (Material Tracking System)</option>
</select>