fix dataTransfer `kind=string`

dist/example.js

@@ -1816,6 +1816,8 @@
 	      return this.add(files);
 	    },
 	    addDataTransfer: function addDataTransfer(dataTransfer) {
+	      var _this = this;
+	
 	      var files = [];
 	      if (dataTransfer.items && dataTransfer.items.length) {
 	        var items = [];
@@ -1834,8 +1836,6 @@
 	        }
 	
 	        return new _promise2.default(function (resolve, reject) {
-	          var _this = this;
-	
 	          var forEach = function forEach(i) {
 	            var item = items[i];
 	

dist/vue-upload-component.js

@@ -1306,6 +1306,8 @@ return /******/ (function(modules) { // webpackBootstrap
 	      return this.add(files);
 	    },
 	    addDataTransfer: function addDataTransfer(dataTransfer) {
+	      var _this = this;
+	
 	      var files = [];
 	      if (dataTransfer.items && dataTransfer.items.length) {
 	        var items = [];
@@ -1324,8 +1326,6 @@ return /******/ (function(modules) { // webpackBootstrap
 	        }
 	
 	        return new _promise2.default(function (resolve, reject) {
-	          var _this = this;
-	
 	          var forEach = function forEach(i) {
 	            var item = items[i];
 	

package.json

@@ -1,7 +1,7 @@
 {
   "name": "vue-upload-component",
   "description": "Vue.js file upload component, Multi-file upload, Upload directory, Drag upload, Drag the directory, Upload multiple files at the same time, html4 (IE 9), `PUT` method, Customize the filter",
-  "version": "2.5.1-beta.1",
+  "version": "2.5.1-beta.2",
   "author": "LianYue",
   "scripts": {
     "dev": "webpack-dev-server --inline --hot",

src/FileUpload.vue

@@ -458,7 +458,7 @@ export default {
           }
         }
 
-        return new Promise(function(resolve, reject) {
+        return new Promise((resolve, reject) => {
           let forEach = (i) => {
             let item = items[i]
             // 结束 或者已有文件了