我有以下JS

function change_ajaxarea1(){
navigator.notification.activityStart();
$('#ajaxarea1').load('http://server.net/droiddev/backbone1/index.php/welcome/', function(){

navigator.notification.activityStop();
$('#ajaxarea1').css("height","auto");
//$('#ajaxarea1').css("overflow","hidden");
});

//navigator.notification.activityStart();
}


function postarticle(){

 $.post("http://server.net/droiddev/backbone1/", { headline: "John", article: "2pm" } );

 }


function addarticle(){

var headlinetemp=$('#headline').val();
var articletemp=$('#article').val();
$.ajax({
type:'POST',
dataType:'json',
url: "http://server.net/droiddev/backbone1/index.php/welcome/addarticle/",
data: { 'headline': headlinetemp, 'article': articletemp},
success:function(){
alert('success');
},
error:function(xhr){
alert(xhr.status);
}



});



}

和以下控制器代码：

  <?php

class Welcome extends CI_Controller {


    public function index()
    {

    $data['query']=$this->site_model->get_last_ten_articles();
$this->load->view('partial1',$data);

    }

    public function addarticle(){

    $headline=$this->input->post('headline');
    $article=$this->input->post('article');
    $this->site_model->insert_entry($headline,$article);



    }
}

addarticle（）javascript
ajax可以运行并将vars发送到服务器并进入db，但是，javascript然后将运行错误函数而不是成功函数。http响应代码是200，我以为它将运行Success函数。有什么建议？