错误

npm ERR! code ENOTFOUND
npm ERR! errno ENOTFOUND
npm ERR! network request to http://registry.npm.taobao.org/math-expression-evaluator failed, reason: getaddrinfo ENOTFOUND registry.npm.taobao.org
npm ERR! network This is a problem related to network connectivity.
npm ERR! network In most cases you are behind a proxy or have bad network settings.
npm ERR! network
npm ERR! network If you are behind a proxy, please make sure that the
npm ERR! network 'proxy' config is set properly.  See: 'npm help config'

原因是镜像的问题，网络好的话，再试一次就行，如果不行的话，更换个镜像就行

如果现在是taobao的镜像，使用下面的

npm config set registry http://registry.cnpmjs.org/

如果不是淘宝的镜像，使用taobao镜像

npm config set registry https://registry.npm.taobao.org