Pass JSON as command line argument to Node

if its a small amount of data, I'd use https://www.npmjs.com/package/minimist, which is a command line argument parser for nodejs. It's not json, but you can simply pass options like

--name=Foo 

or

-n Foo

I think this is better suited for a command line tool than json.

If you have a large amount of data you want to use you're better of with creating a json file and only pass the file name as command line argument, so that your program can load and parse it then.

Big objects as command line argument, most likely, aren't a good idea.

this works for me:

$ node foo.js --json-array='["zoom"]'

then in my code I have:

  import * as _ from 'lodash';

  const parsed = JSON.parse(cliOpts.json_array || []);

  _.flattenDeep([parsed]).forEach(item => console.log(item));

I use dashdash, which I think is the best choice when it comes to command line parsing.

To do the same thing with an object, just use:

$ node foo.js --json-object='{"bar": true}'

This might be a bit overkill and not appropriate for what you're doing because it renders the JSON unreadable, but I found a robust way (as in "works on any OS") to do this was to use base64 encoding.

I wanted to pass around lots of options via JSON between parts of my program (a master node routine calling a bunch of small slave node routines). My JSON was quite big, with annoying characters like quotes and backslashes so it sounded painful to sanitize that (particularly in a multi-OS context).

In the end, my code (TypeScript) looks like this:

in the calling program:

const buffer: Buffer = new Buffer(JSON.stringify(myJson));
const command: string = 'node slave.js --json "' + buffer.toString('base64') + '" --b64';
const slicing: child_process.ChildProcess = child_process.exec(command, ...)

in the receiving program:

let inputJson: string;
if (commander.json) {
  inputJson = commander.json;
  if (commander.b64) {
    inputJson = new Buffer(inputJson, 'base64').toString('ascii');
  }
}

(that --b64 flag allows me to still choose between manually entering a normal JSON, or use the base64 version, also I'm using commander just for convenience)