nvm use (may need to nvm install 9), cd to a day, npm install, and run of the scripts via npm run:
$ cd 01
$ nvm use
Found '/Users/vanhornj/dev/advent-of-code-2017/.nvmrc' with version <9>
Now using node v9.2.0 (npm v5.5.1)
$ npm install
...
$ npm run
Scripts available in 01 via `npm run-script`:
parts
node index.js
$ npm run parts
> 01@1.0.0 parts /Users/vanhornj/dev/advent-of-code-2017/01
> node index.js
sum, adjacent: 1390
sum, halfway: 1232