refactor:提取获取文件后缀函数

src/api/modules/file.ts

 import axios from '@/utils/http';
 const base = process.env.VUE_APP_SERVER + '/file';
+function getFileSuffix(file: File) {
+    const fileName = file.name;
+    const index = fileName.lastIndexOf('.');
+    return fileName.substr(index + 1);
+}
 export default {
     upload(file: File, cb: (progressEvent: any) => void = (progressEvent: any) => progressEvent) {
+        const suffix = getFileSuffix(file);
         const formData = new FormData();
-        const filename = file.name;
-        const index = filename.lastIndexOf('.');
-        const suffix = filename.substr(index + 1);
         formData.append('file_data', file);
         return axios({
             url: `${base}/upload?file_type=${suffix}`,