print selected JSON data on console

json.js

#!/usr/bin/env node

/**
 * print selected JSON data on console
 *
 * using files
 * 
 *   curl https://registry.npmjs.com/mergee > /tmp/j
 *   json /tmp/j versions 0.2.3 name
 *
 * piping from stdin
 * 
 *   curl https://registry.npmjs.com/mergee | json -- versions 0.2.3 name
 * 
 * @license MIT
 */

var path = require('path')
var fs = require('fs')
var args = process.argv.slice(2)

main()

function _get (obj, keys) {
  var tmp = obj
  if (keys) {
    for (var i = 0; i < keys.length; i++) {
      var key = keys[i]
      if (tmp && tmp.hasOwnProperty(key)) {
        tmp = tmp[key]
      }
      else {
        return undefined
      }
    }
  }
  return tmp
}

function out (str) {
  if (args.length === 1) {
    args = args[0].split('.')
  }
  var data = _get(JSON.parse(str), args)
  console.log(JSON.stringify(data, null, 2))
}

function main () {
  var str = ''
  if (args.length && args[0] !== '--') {
    var file = path.resolve(process.cwd(), args.shift())
    var str = fs.readFileSync(file, 'utf8')
    out(str)
  } else {
    args.shift()
    process.stdin.setEncoding('utf8');
    process.stdin.on('readable', () => {
      var chunk = process.stdin.read()
      if (chunk !== null) str += chunk
    })
    process.stdin.on('end', () => {
      out(str)
    })
  }
}