Error message
npm ERR! errno ETIMEDOUT
npm ERR! network request to https://registry.npmjs.org/nprogress failed, reason: connect ETIMEDOUT 104.16.22.35:443
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'
Solution: Use cnpm mirror
npm install -g cnpm --registry=https://registry.npm.taobao.org