error Received malformed response from registry for undefined. The registry may be down.

Laravel 学习中

https://laravel-china.org/courses/laravel-essential-training-5.5/569/style-beautification

执行下列代码时报错

$ yarn install --no-bin-links
$ yarn add cross-env

error Received malformed response from registry for undefined. The registry may be down.

解决方法：删除 package.json 下的 4 处 cross-env；（注意 JSON 格式）

再次执行