!DOCTYPE html>
html>
 head>
 meta charset="UTF-8">
 title>ajax交互/title>
 script src="//cdn.bootcss.com/jquery/3.1.1/jquery.min.js">/script>
 script>
  $('.but').click(function () {
    var formData = $("#myform").serialize();//formData值：account=sdfpasswd=sdf
    //serialize() 方法通过序列化表单值，创建 URL 编码文本字符串,这个是jquery提供的方法
    $.ajax({
      type: "post",
      url: "{:url('index/index/reg')}", //数据传输的控制器方法
      data: formData,//这里data传递过去的是序列化以后的字符串
      success: function (data) {
        console.log(data);
        $("#content").append(data);//获取成功以后输出返回值
      }
    });
    return false;
  })
/script>
 /head>
 body>
 form id="myform">
  !--这里给表单起个id用于获取表单并序列化-->
  input type="text" name="account" />
  input type="password" name="passwd" />
  input type="button" value="提交" class="but">
 /form>
 div id="content">
 /div>
 /body>
/html>

public function reg($account,$passwd){
 if($account == '123'){
  return json("ajax成功！".$account."---".$passwd);
 }else{
  return json("你输出的是其他值：".$account."---".$passwd);
 }
}

!doctype html>
html lang="en">
head>
  meta charset="UTF-8">
  title>管理员登录/title>
  meta name="renderer" content="webkit|ie-comp|ie-stand">
  meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
  meta name="viewport"
     content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=0">
  meta http-equiv="Cache-Control" content="no-siteapp"/>
  link rel="shortcut icon" href="./favicon.ico" rel="external nofollow" type="image/x-icon"/>
  link rel="stylesheet" href="./static/css/font.css" rel="external nofollow" >
  link rel="stylesheet" href="./static/css/weadmin.css" rel="external nofollow" >
  script src="./lib/layui/layui.js" charset="utf-8">/script>
/head>
body class="login-bg">
div class="login">
  div class="message">管理登录/div>
  div id="darkbannerwrap">/div>
  form method="post" class="layui-form">
    input name="username" placeholder="用户名" type="text" lay-verify="required" class="layui-input">
    hr class="hr15">
    input name="password" lay-verify="required" placeholder="密码" type="password" class="layui-input">
    hr class="hr15">
    input class="loginin" value="登录" lay-submit lay-filter="login" style="width:100%;" type="submit">
    hr class="hr20">
  /form>
/div>
script src="./static/js/jquery-3.3.1.min.js">/script>
script type="text/javascript">
  layui.extend({
    admin: '{/}./static/js/admin'
  });
  //layui.use调用模块
  layui.use(['form', 'admin'], function () {
    //获得form模块
    var form = layui.form
      , admin = layui.admin;
    //监听提交
    //事件监听
    //语法：form.on('event(过滤器值)', callback);（过滤器值指lay-filter="过滤器值"）
    //function(data)里的data是一个object，data.field是表单填写的内容
    form.on('submit(login)', function (data) {
      //$.post写法：$(selector).post(URL,data,function(data,status,xhr),dataType)
      var post_data = data.field;
      $.post("{:url('verify')}"
        , post_data
        , function (data) {
          console.log(data);
        }
      )
      return false;
    });
  })
  ;
/script>
!-- 底部结束 -->
/body>

 public function verify()
  {
    $posts = input("post.password");
    return json($posts);
  }