cyclic reference.js

'use strict';
const util = require("util");

let foo = {};
let bar = {};

foo.ref = bar;
bar.ref = foo;

console.log(JSON.stringify(foo));
//TypeError: Converting circular structure to JSON        
console.log(util.inspect(foo, { showHidden: true, depth: null }));
//{ ref: { ref: [Circular] } }

///////////////////////
let foo = {

};
let bar = function () {
    this.ref = foo;
};

foo.ref = bar;
console.log(JSON.stringify(foo));
//{}  
console.log(util.inspect(foo, { showHidden: true, depth: null }));
//{ ref:                                                                                                                              
//    { [Function]                                                                                                                     
//      [length]: 0,                                                                                                                   
//      [name]: '',                                                                                                                    
//      [prototype]: { [constructor]: [Circular] } } }                                                                                 


'use strict';
const util = require("util");
const EventEmitter = require('events');

class Foo extends EventEmitter{}

let foo = new Foo();

foo.on("bar", function barHandler(){
    foo.bar = "bar";
})

console.log(JSON.stringify(foo));
//{"domain":null,"_events":{},"_eventsCount":1} 
console.log(util.inspect(foo, { showHidden: true, depth: null }));
// Foo {                                                                                                                               
//   domain: null,                                                                                                                     
//   _events:                                                                                                                          
//    { bar:                                                                                                                           
//       { [Function: barHandler]                                                                                                      
//         [length]: 0,                                                                                                                
//         [name]: 'barHandler',                                                                                                       
//         [prototype]: barHandler { [constructor]: [Circular] } } },                                                                  
//   _eventsCount: 1,                                                                                                                  
//   _maxListeners: undefined }