npm install xlsx --save
npm install file-saver --save

package.json

"file-saver": "^2.0.5",
"xlsx": "^0.18.3"

版本不兼容导致"export default (imported as 'XLSX') was not found in 'xlsx'

先卸载：npm uninstall xlsx

之后重新安装低版本：npm install xlsx@0.17.0 --save