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：

<scripttype="text/javascript"src="jquery-3.2.1.js"></script><scripttype="text/javascript"src="jquery.validate.min.js"></script>//引入的插件<scripttype="text/javascript">$(document).ready(function(){formValidate();//表单验证函数});functionformValidate(){$("#sendmail").validate({//#sendmail表单iderrorElement:"span",//错误信息将放入此标签内errorClass:"error_input",//验证出错时使用的cssclasssuccess:"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：formform.submit();//提交表单}});};</script><styletype="text/css">.error_input{color:red;}//错误提示的样式</style><formaction="#"method="post"id="sendmail"name="sendmail"><p>发件邮箱：<inputid="from"placeholder="银行账号"name="from"type="email"required/><span></span></p><p>发件姓名：<inputid="fromName"placeholder="银行账号"name="fromName"type="text"required/><span></span></p><p>收件邮箱：<inputid="to"placeholder="银行账号"name="to"type="email"required/><span></span></p><p>url：<inputid="url"name="url"placeholder="银行账号"type="email"required/><span></span></p><p>发件主题：<inputid="subject"placeholder="银行账号"name="subject"type="text"required/><span></span></p><p>选择类别：<selectid="contry"name="contry"><optionvalue="中国">中国</option><optionvalue="美国">美国</option><optionvalue="日本">日本</option><optionvalue="俄罗斯">俄罗斯</option><optionvalue="法国">法国</option><optionvalue="德国">德国</option></select><span></span></p><p>邮件内容：<textareaid="html"placeholder="银行账号"name="html"cols="120"rows="6"required></textarea><span></span></p><p>附　　件：<inputname="submit"type="submit"value="提交"/></p></form>