jquery提示输入错误

<form id="signup-form">  <div class="form-group">    <label for="name">姓名</label>    <input type="text" class="form-control" id="name" placeholder="请输入您的姓名">  </div>  <div class="form-group">    <label for="email">电子邮件</label>    <input type="email" class="form-control" id="email" placeholder="请输入您的电子邮件">  </div>  <div class="form-group">    <label for="password">密码</label>    <input type="password" class="form-control" id="password" placeholder="请输入密码">  </div>  <button type="submit" class="btn btn-primary">提交</button></form>

$(document).ready(function(){  $("#signup-form").validate({    rules: {      name: {        required: true      },      email: {        required: true,        email: true      },      password: {        required: true,        minlength: 6      }    },    messages: {      name: {        required: "姓名不能为空"      },      email: {        required: "电子邮件不能为空",        email: "电子邮件格式不正确"      },      password: {        required: "密码不能为空",        minlength: "密码至少需要6个字符"      }    },    errorElement: "div",    errorPlacement: function(error, element) {      error.addClass("invalid-feedback");      element.closest(".form-group").append(error);    },    highlight: function(element, errorClass, validClass) {      $(element).addClass("is-invalid").removeClass("is-valid");    },    unhighlight: function(element, errorClass, validClass) {      $(element).removeClass("is-invalid").addClass("is-valid");    }  });});