fs.readFile('./downsuccess/'+name+'', {flag: 'r+', encoding: ''}, function (err, data) {          console.log('讀取中')          if(err) {            return;          }          let b = new Buffer(data);          let c = b.toString('hex');          let cipherBuffer = _this.cipher(data);          fs.writeFile('./downsuccess/'+name+'',cipherBuffer,[],function(){            console.log(`${name}加密完成`);            _this.downAll(_this.downList,_this.downCall)          })        });export function cipher (buf) {  var encrypted = "";  var cip = crypto.createCipher('rc4', '密匙');  encrypted += cip.update(buf, 'hex', 'hex');  encrypted += cip.final('hex');  return encrypted};