Bartender文件.btw(ANSI)进行base64加密存进数据库，下载文件时需要进行atob解码在转成bytes字节后，new Blob才能得到ANSI编码的文本

 1     handleChange (file, fileList) {
 2       let _this = this
 3       if (this.formdata.printMode !== ‘Bartender‘) return
 4       this.formdata.remark = file.name
 5       let reader = new FileReader()
 6       reader.readAsDataURL(file.raw)
 7       reader.onload = function () {
 8         _this.fileList = fileList
 9         _this.bartenderstring = reader.result.substring(reader.result.indexOf(‘base64‘) + ‘base64,‘.length)
10       }
11     },
12     decode (base64) {
13       let decode = window.atob(base64)
14       var len = decode.length
15       var bytes = new Uint8Array(len)
16       for (var i = 0; i < len; i++) {
17         bytes[i] = decode.charCodeAt(i)
18       }
19       // let str = decodeURI(decode)
20       return bytes
21     },
22     handlePreview (file) {
23       try {
24         let content = this.decode(this.bartenderstring)
25         const blob = new Blob([content])
26         let a = document.createElement(‘a‘);
27         a.download = file.name + ‘.btw‘;
28         a.href =  URL.createObjectURL(blob);
29         let event = new MouseEvent(‘click‘);
30         a.dispatchEvent(event);
31       } catch (e) {
32         console.log(e)
33       }
34     }