如何使用jQuery验证插件在keyup上验证非表单元素中的输入

$(function() {
  $('.form-container').validate({
    rules: {
      useremail: {
        required: true,
        email: true
      },
      userstate: {
        required: true,
        maxlength: 2
      }
    },
    messages: {
      useremail: 'Please enter a valid email',
      userstate: 'Please enter your state',
    }
  });
  
  $('.form-container input').on('keyup', function() {
    $(this).validate();
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-validate/1.18.0/jquery.validate.min.js"></script>

<div class="form-container">
  <input type="text" name="useremail" placeholder="Email" />
  <input type="text" name="userstate" placeholder="State" maxlength="2" />
</div>