Jquery 当用户选择图像而不提交时，如何使任何图像自动上载？

我正在使用Codeigniter和jQueryAjax创建自动上传图像的功能。用户将从他们的计算机中选择他们的图像，然后Ajax将通过Post发送到服务器

问题：图像无法上传到服务器，在Ajax响应后，我得到一个空的图像属性。似乎我的表格无效，但我仍然找不到解决方案

结果：Ajax响应后，我的res变量无法获取任何数据

这是我的控制器

public function upload() {

        $this->load->helper(array('form', 'url'));
        $config['upload_path'] = './uploads/';
        $config['image_library'] = 'gd2';
        $config['allowed_types'] = 'gif|jpg|png';
        $config['max_size'] = '100';
        $config['max_width'] = '1024';
        $config['max_height'] = '768';
        $this->load->library('upload', $config);
        $token = $this->security->get_csrf_hash();
        $data = array();
        $res = FALSE;
        if (!$this->upload->do_upload('userfile')) {
//            $data = $this->upload->data();
            $res = FALSE;
        } else {

            $res = TRUE;
            $this->upload->do_upload('userfile');
            $data = $this->upload->data();
        }
        echo json_encode(array('res'=>$res,'img_pro'=>$data,'token'=>$token));
    }

这是我的表格

<?php echo form_open_multipart('image/upload', array("class" => "form_horizontal", "id" => "images")); ?> 
<div class="col-lg-12 col-sm-12 col-xs-12 ">
    <div class="control-group" style="margin-top: 12px;height: 70px; width:100%;border:1px solid red;">
       <div class="controls form-group-sm">
            <span class="btn btn btn-success btn-lg btn-file">
            Select your images: <?PHP echo form_upload('userfile', '', 'id="userfile" class="userfile"') ?>
             </span>
          </div>
       </div>
    </div> 
 <?php echo form_close(); ?>

---

$userfile.val提供一个字符串，因此您不上传文件，而是上传其路径，这就是为什么上传失败的原因

<script type="text/javascript">
    $(document).ready(function () {
        $("#images input[name=userfile]").change(function () {
                $.ajax({
                    type: "post", 
                    url: "<?php echo base_url('image/upload'); ?>",
                    data: {
                        '<?PHP echo $this->security->get_csrf_token_name(); ?>': '<?PHP echo $this->security->get_csrf_hash(); ?>',
                        userfile: $("#userfile").val()
                    },
                    dataType: "json",
                    cache: false,
                    success: function (data) {
                        console.log(data);
                        console.log($("#userfile").val());
                    }
                }); 
        });
    });
</script>

{
  "res":false,
  "img_pro":{
    "file_name":"",
    "file_type":"",
    "file_path":".\/uploads\/",
    "full_path":".\/uploads\/",
    "raw_name":"",
    "orig_name":"",
    "client_name":"",
    "file_ext":"",
    "file_size":null,
    "is_image":false,
    "image_width":null,
    "image_height":null,
    "image_type":"",
    "image_size_str":""
  },
  "token":"7a3f48fc1d4bec708e2ab338ddf96038"
}

$("#userfile").change(function (objEvent) {
    var objFormData = new FormData();
    // GET FILE OBJECT
    var objFile = $(this)[0].files[0];
    // APPEND CSRF TOKEN TO POST DATA
    objFormData.append('<?= $this->security->get_csrf_token_name(); ?>', '<?= $this->security->get_csrf_hash(); ?>');
    // APPEND FILE TO POST DATA
    objFormData.append('userfile', objFile);
    $.ajax({
        url: "<?= base_url('image/upload'); ?>",
        type: 'POST',
        contentType: false,
        data: objFormData,
        //JQUERY CONVERT THE FILES ARRAYS INTO STRINGS.SO processData:false
        processData: false,
        success: function (data) {
        }
    });
});