Those of you upgrading npm to its latest version, firstname.lastname@example.org, might notice that it installs a new binary alongside the usual npm: npx.
For the past couple of years, the npm ecosystem has been moving more and more towards installing tools as project-local devDependencies, instead of requiring users to install them globally. This means that tools like mocha, grunt, and bower, which were once primarily installed globally on a system, can now have their versions managed on a per-project basis. It also means that all you need to do to get an npm-based project up and running is to make sure you have node+npm on your system, clone the git repo, and do npm it to run install and test. Since npm run-script adds local binaries to path, this works just fine!