Recursively Print Javascript Object

printObject.js

'use strict';

const printObject = (obj, seen = [], level = 0) => {
    if (seen.length === 0) {
        seen.push(obj);
    }

    const indent = "  ".repeat(level);

    for (let k in obj) {
        // It is possible object is not derived from Object.prototype
        if(Object.prototype.hasOwnProperty.call(obj, k)) {
            const v = obj[k];

            if (v == null) {
                console.log(indent + k + ': null');
            }
            else if (Array.isArray(v)) {
                //console.log(indent + k + ': [' + v + ']');
                console.log(indent + k + ': [');
                printObject(v, seen, level + 1);
                console.log(indent + ']')
            }
            else if (typeof v === 'function') {
                console.log(indent + k + ': [Function]');
            }
            else if (typeof v === 'object') {
                if (seen.indexOf(v) >= 0) {
                    console.log(indent + k + ': [CIRCULAR]');
                }
                else {
                    seen.push(v);
                    console.log(indent + k + ': {');
                    printObject(v, seen, level + 1);
                    console.log(indent + '}')
                }
            }
            else {
                console.log(indent + k + ': ' + v);
            }
        }
    }
};
module.exports.printObject = printObject;