Read about a proxy variable in a .npmrc file but it does not work. Trying to avoid manually downloading all require packages and installing.
Though there are already many good advice, for my environment(Windows 7, using PowerShell) and the last version available of node.js ( v8.1.2 ) all the above did not worked, except when I followed brunowego settings.
So check your settings with :
npm config list
Settings behind a proxy:
npm config set registry http://registry.npmjs.org/
npm config set http-proxy http://username:password@ip:port
npm config set https-proxy http://username:password@ip:port
npm config set proxy http://username:password@ip:port
npm set strict-ssl false
Hope this will save time to someone