tricks.md

Parsing Tricks

Stop Parsing

Use -- to stop parsing flags and stuff the remainder into argv._.

$ node examples/reflect.js -a 1 -b 2 -- -c 3 -d 4
{ _: [ '-c', '3', '-d', '4' ],
  a: 1,
  b: 2,
  '$0': 'examples/reflect.js' }

Negating Boolean Arguments

If you want to explicitly set a field to false instead of just leaving it undefined or to override a default you can do --no-key.

$ node examples/reflect.js -a --no-b
{ _: [], a: true, b: false, '$0': 'examples/reflect.js' }

Numbers

Every argument that looks like a number (!isNaN(Number(arg))) is converted to one. This way you can just net.createConnection(argv.port) and you can add numbers out of argv with + without having that mean concatenation, which is super frustrating.

Arrays

If you specify a flag multiple times it will get turned into an array containing all the values in order.

$ node examples/reflect.js -x 5 -x 8 -x 0
{ _: [], x: [ 5, 8, 0 ], '$0': 'examples/reflect.js' }

You can also configure an option as the type array, to support arrays of the form -x 5 6 7 8.

Objects

When you use dots (.s) in argument names, an implicit object path is assumed. This lets you organize arguments into nested objects.

$ node examples/reflect.js --foo.bar.baz=33 --foo.quux=5
{ _: [],
  foo: { bar: { baz: 33 }, quux: 5 },
  '$0': 'examples/reflect.js' }