Jq Bootstrap 多选 - 必须至少选择一个值

Question

我使用 jq bootsrtrap 多选，我需要一个必须选择至少一个值的选择。怎么做？

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css">

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-multiselect/0.9.15/css/bootstrap-multiselect.css">

<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js"></script>

<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js"></script>

<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js"></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-multiselect/0.9.15/js/bootstrap-multiselect.min.js"></script>

<select id="select-records" multiple="multiple" class="form-control">

    <option value="0">0</option>

    <option value="50">50</option>

    <option value="500">500</option>

</select>

$('#select-records').multiselect({

  maxHeight: 400,

  buttonWidth: '100%',

  onChange: function (element, checked) {

  // ...

  }

});

Answer 1

$("#select-records").val() 返回所选值的数组if($("#select-records").val().length == 0){alert("You must select at least one option");}如果你想在 chage 事件中使用$( "#select-records" ).change(function() {if($("#select-records").val().length == 0){alert("You must select at least one option");}});