gistfile1.txt

> a = {}; b = {next: a}; c = {next: b}; d = {next:c}; a.next = d
{ next: { next: { next: [Object] } } }
> a
{ next: { next: { next: [Object] } } }
> JSON.stringify(a)
TypeError: Converting circular structure to JSON
    at Object.stringify (native)
    at repl:1:7
    at REPLServer.self.eval (repl.js:111:21)
    at Interface.<anonymous> (repl.js:250:12)
    at Interface.EventEmitter.emit (events.js:88:17)
    at Interface._onLine (readline.js:199:10)
    at Interface._line (readline.js:517:8)
    at Interface._ttyWrite (readline.js:735:14)
    at ReadStream.onkeypress (readline.js:98:10)
    at ReadStream.EventEmitter.emit (events.js:115:20)
> function del(x) { delete x; console.log(++del.count); }; del.count = 0
0
> entry = c; cur = entry.next; while (cur != entry) { next = cur.next; del(cur); cur = next } del(entry)
1
2
3
4
undefined
>