NodeJS JSON prettifier for REST piping on the console

jsonpr.js

'use strict';
/**
 * JSON prettifier
 *
 * as a general prettifier `node jsonpr.js '{"this":"is","json":"prettifier"}'`
 * as a stream reader `echo '{"some":"JSON"}' | node jsonpr.js`
 */
process.stdin.setEncoding('utf8');
let stdin = process.openStdin();
let json = process.argv[2];
let spaces = 4;

if (process.argv[3]) {
    spaces = parseInt(process.argv[3]);
}

function logJSONString(json) {
    let jsonObj = JSON.parse(json);
    let jsonString = JSON.stringify(jsonObj, null, spaces);
    console.log(jsonString);
}

if (json) {
    logJSONString(json);
    process.exit();
}

stdin.on('data', function(chunk) {
    logJSONString(chunk);
});