jquery 按钮预览图片功能的代码，我看不太懂。应该怎么学
<?php
namespace app\admin\controller;
use app\admin\controller\Common;
use app\admin\model\NewsModel;
use app\admin\model\NewsPicModel;
use think\facade\Request;
use think\facade\Session;
class NewsPic extends Common
{
public function index()
{
//实例化模型
$newPic = new NewsPicModel();
$pics = $newPic->order('id', 'desc')->paginate(6);
$this->view->pics = $pics;
// 渲染新闻缩略图列表
return $this->fetch();
}
public function add()
{
// 查询所有新闻数据
$news = NewsModel::all();
//将数据赋值给模板
$this->view->news = $news;
// 渲染新闻缩略图添加界面
return $this->fetch();
}
public function upload()
{
// 获取上传图片的信息
$file = Request::file('file');
// 验证图片并移动到指定目录
if ($info = $file->validate(['ext' => 'jpg,jpeg,png,gif'])->move('upload')) {
// 拼接图片路径
$fileName = '/upload/' . $info->getSaveName();
// 返回上传成功的提示信息
return json([1, '上传成功！', 'data' => $fileName]);
} else {
// 返回上传失败的错误信息
return $file->getError();
}
}
public function DoAdd()
{
// 获取提交的数据
$data = Request::param();
$data['time'] = time();
$data['username'] = Session::get('username');
$newPic = new NewsPicModel();
if ($newPic->save($data)) {
return ['res' => 1, 'msg' => '发布成功！'];
} else {
return ['res' => 0, 'msg' => '发布失败！'];
}
}
public function del()
{
$picId=Request::param('id');
$newPic = new NewsPicModel();
if ($newPic->destroy($picId)){
return ['res'=>1];
}
}
}