验证用户名，密码，验证码，发送alax请求进行登录代码

 //html代码
 <div class="layui-form" id="larry_form">
              <div class="layui-form-item">
                    <label class="layui-form-label">用户名:</label>
                    <input type="text" name="userName" required  lay-verify="" autocomplete="off" class="layui-input larry-input userName" placeholder="请输入您的用户名">
              </div>
              <div class="layui-form-item" id="password">
                    <label class="layui-form-label">密码:</label>
                    <input type="password" name="password" required lay-verify="password" autocomplete="off" class="layui-input larry-input psw" placeholder="请输入您的登录密码">
              </div>
              <div class="layui-form-item larry-verfiy-code" id="larry_code">
                     <input type="text" id="code" name="code" lay-verify="" autocomplete="off" maxlength="4" class="layui-input larry-input " placeholder="输入验证码" >
                     <div class="code">
                            <div class="arrow" style="opacity:0.6;filter:alpha(opacity=60);"></div>
                            <div class="code-img"><img src="/randomCode" alt="" class="layui-disabled" style="opacity:0.6;filter:alpha(opacity=60);" id="codeimage" disabled="disabled"></div>
                            <a id="change" class="change" style="opacity:0.6;filter:alpha(opacity=60);" title="看不清,点击更换验证码"><i></i></a>
                     </div>
              </div>

              <div class="layui-form-item">
                   <button class="layui-btn larry-btn submit" lay-filter="submit" lay-submit>立即登录</button>
              </div>
         </div>

     $(document).keydown(function(event){
         if(event.keyCode==13){
             $(".submit").click();
         }
     });
     $('.submit').click(function(){
        var userName = $('.userName').val();
         var psw = $('.psw').val();
         var code = $('#code').val();
         if(userName.trim()==''){
             layer.alert("用户名不能为空！", {icon: 2,title:'提示'});
             return;
         }
         if(psw.trim()==''){
             layer.alert("密码不能为空！", {icon: 2,title:'提示'});
             return;
         }
         // if(code.trim()==''){
         //     layer.alert("验证码不能为空！", {icon: 2,title:'提示'});
         //     return;
         // }
        $.ajax({
            type: "post",
            url: "/login",
            // data: "userName="+userName+"&password="+psw+"&code="+code,
            data: "userName="+userName+"&password="+psw,
            success: function (data) {
                var message = data.msg;
                if(data.code === '0'){
                    layer.msg(message, {icon: 1, time: 1000});
                    setTimeout(function () {
                        window.location.href = 'index.html';
                     }, 1000);
                } else {
                    layer.alert(message, {
                        icon: 2,title:'提示'
                    });
                    // $('.userName').val('');
                    // $('.psw').val('');
                    // $('#code').val('');
                    // // $("#codeimage").attr("src", '/randomCode?t=' + Math.random());
                    return;
                }
            },
            error: function () {
            }
        })
     })