表单验证提示插件validate

此表单验证插件会对表单字段进行验证，实时提示用户输入信息，用户体验非常好，验证提示紧随input框！

以下为表单验证案例代码：

<script type="text/javascript" src="jquery-3.2.1.js"></script> <script type="text/javascript" src="jquery.validate.min.js"></script>    //引入的插件 <script type="text/javascript">     $(document).ready(function(){         formValidate();                               //表单验证函数     });     function formValidate(){         $("#sendmail").validate({                      //#sendmail表单id             errorElement : "span",                     //错误信息将放入此标签内             errorClass: "error_input" ,                //验证出错时使用的css class             success: "valid" ,                         //自定义验证成功时的动作             errorPlacement: function(error, element) { //自定义错误消息的显示位置                 element.next().html(error);     //error错误信息，element错误产生的input             },                 rules: {                     "from":{                         required: true                     },                     "fromName":{                         required: true                     },                     "to":{                         required: true                     },                     "url":{                         required: true                     },                     "subject":{                         required: true                     },                     "html":{                         required:true                     },                     "contry":{                         required:true                     }                 },             messages: {                 "from":{                     required: '请输入公司名称'                 },                 "fromName":{                     required: '请选择省份'                 },                 "to":{                     required: '请选择城市'                 },                 "url":{                     required: '请选择县/区'                 },                 "subject":{                     required: '请输入地址'                 },                 "html":{                     required:'请选择国家区号'                 },                 "contry":{                     required:'请选择国家区号'                 }             },             submitHandler: function(form){ //表单提交句柄,为一回调函数，带一个参数：form                 form.submit();    //提交表单             }         });     }; </script> <style type="text/css">     .error_input{color:red;}                         //错误提示的样式 </style> <form action="#" method="post" id="sendmail" name="sendmail">     <p>发件邮箱：<input id="from" placeholder="银行账号"  name="from" type="email" required/><span></span></p>     <p>发件姓名：<input id="fromName" placeholder="银行账号" name="fromName" type="text" required/><span></span></p>     <p>收件邮箱：<input id="to" placeholder="银行账号" name="to" type="email" required/><span></span></p>     <p>url：<input id="url" name="url" placeholder="银行账号" type="email" required/><span></span></p>     <p>发件主题：<input id="subject" placeholder="银行账号" name="subject" type="text" required/><span></span></p>     <p>选择类别：<select id="contry" name="contry">             <option value ="中国">中国</option>             <option value ="美国">美国</option>             <option value="日本">日本</option>             <option value="俄罗斯">俄罗斯</option>             <option value="法国">法国</option>             <option value="德国">德国</option>         </select>         <span></span></p>     <p>邮件内容：<textarea id="html" placeholder="银行账号" name="html" cols="120" rows="6" required></textarea><span></span></p>     <p>附　　件：<input name="submit" type="submit" value="提交"/></p> </form>