Firstly, you should go and read how to use NPM as a build tool. Then come back here and explore the repository. It's fairly standard, and the bare minimum to show you what a complex config would look like.
See some areas for optimising? Great! Send a PR, I'm definitely interested in seeing some great ways to optimise this.
Several scripts use the npm -s flag to silence npm's output from the subtasks, which makes the log output a little tidier (it is a shortcut for --loglevel=silent, read more on npms documentation for flags: https://docs.npmjs.com/misc/config#default-configs).