javascript - 多个复选框 > 至少应显示一条必填项，否则会显示错误消息

Question

如何确保访问者在提交表单之前至少勾选/选择一个选项？

这是我的代码的摘录:

<div class="col-md-6" id="ajax_succs">
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="351">Option 1</div>
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="353">Option 2</div>
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="354">Option 3</div>
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="355">Option 4</div>
...

Answer 1

找到checked 输入的length。尝试以下操作:

$('#btnSubmit').click(function(){
    var chkSelected = $('input:checked').length;
    if(chkSelected <= 0){
        console.log('No checkbox selected');
    }
    else{
        console.log('Checkbox selected');
    }
})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="351">Option 1</div>
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="353">Option 2</div>
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="354">Option 3</div>
<div class="check_parent">
<input type="checkbox" name="sub_sub_cat_select[]" class="default_checkbox" value="355">Option 4</div><br>
<input type="submit" id="btnSubmit" name="" value="Submit">