node

Installs a node binary into your project, which because npm runs scripts with the local ./node_modules/.bin in the PATH ahead of the system copy means you can have a local version of node that is different than your system's, and manage node as a normal dependency.
Warning: don't install this globally with npm 2. npm@2 immediately removes node, then can't run the scripts that make this work.

Use

npm i node@lts

Use with npx

npx node@4 myscript.js

This will run myscript.js with the latest version of node from the v4 major.
Using the shell auto-fallback of npx, you can even do it like so:

node@4 myscript.js

Thanks

Major thanks to Kat Marchán for late-night problem solving, and to CJ Silverio and Maciej Małecki for egging me on way back when I had the idea to package node up this way. It does turn out if you ask "why not?!" once in a while something fun happens.