js is a a better alternative to node -p. It will automatically convert data from and to JSON string representations, and will automatically expose enviroment variables as globals preceded with $.

Usage

js <javascript>

Examples

Using math

js 2+2

Read a field from a JSON file

js stdin.version < package.json

Add a field to a JSON file on the fly

js 'stdin.foo = "bar", stdin' < in.json > out.json