EXTJS如何进行上传文件判断

{

                         xtype: 'textfield',

                         id: 'imgFileEidt',

                         name: 'imgFileEidt',

                         inputType: "file",

                         labelWidth: 60,

                         fieldLabel: '上传照片',

                         regex: '',//图片验证正则表达式

                         listeners: {

                             'change': function () {

                             }

                         },

                         msgTarget: 'under',

                         validator: function (value) {

                             var panduan = value.split('.');

                             if (panduan[panduan.length - 1] == 'jpg') {

                                 return true;

                             }

                             else {

                                 return "上传文件必须是jpg, jpeg类型文件中的一种！";
                             }

}

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