example pre-ES6 (should work on ES3) code to check for recursion (to debug why JSON serialisation breaks)

checkRecursion.js

// example pre-ES6 (should work on ES3) code to check for recursion (to debug why JSON serialisation breaks)
// Ⓕ CC0 by mirabilos

var subs = {
	"miau": ["mrr", "purr"],
	"mrr": [],
	"mraw": {},
	"f": false,
	"t": true,
	"n": null,
	"r": { "recursive": false }
};

var object = {
	aProperty: {
		aSetting1: 1,
		aSetting2: 2,
		aSetting3: 3,
		aSetting4: 4,
		aSetting5: 5
	},
	bProperty: {
		aFuckup: subs,
		bSetting1: {
			bPropertySubSetting: true
		},
		bSetting2: "bString"
	},
	cProperty: {
		cSetting: "cString"
	}
};

function checkRecursive(obj, valmap, reckey, recpath, key='', pfx='top') {
	if (valmap === undefined)
		valmap = {};
	if (reckey === undefined) {
		reckey = [];
		recpath = [];
	}
	var rv = [];

	if (obj && typeof(obj) === "object" &&
	    typeof(obj.toJSON) === "function")
		obj = obj.toJSON(key);

	switch (typeof(obj)) {
	case "string":
	case "number":
	case "boolean":
	case "null":
		valmap[pfx] = "v:" + obj;
		break;
	case "object":
		if (!obj) {
			valmap[pfx] = "null";
			break;
		}
		// Array or Object

		var recidx = Array.prototype.indexOf.call(reckey, obj);
		if (recidx != -1) {
			valmap[pfx] = "recurses:" + recpath[recidx];
			rv.push(recpath[recidx]);
			break;
		}
		Array.prototype.push.call(reckey, obj);
		Array.prototype.push.call(recpath, pfx);

		if (Object.prototype.toString.apply(obj) === "[object Array]") {
			valmap[pfx] = "[]";
			var len = obj.length;
			for (var i = 0; i < len; ++i) {
				var r = checkRecursive(obj[i], valmap,
				    reckey, recpath, i, pfx + '[' + i + ']');
				if (r !== false)
					rv = rv.concat(r);
			}
			break;
		}

		valmap[pfx] = "{}";
		for (var okey in obj)
			if (Object.prototype.hasOwnProperty.call(obj, okey)) {
				var r = checkRecursive(obj[okey], valmap,
				    reckey, recpath, okey, pfx + '.' + okey);
				if (r !== false)
					rv = rv.concat(r);
			}
		break;
	default:
		valmap[pfx] = "?:" + typeof(obj);
		break;
	}
	return rv.length ? rv : false;
}

var vmap;
var isrec;

vmap = {};
isrec = checkRecursive(object, vmap);
console.log("object (1) is " + (isrec === false ? "ok" : "recursive"));
for (var k in vmap)
	if (vmap.hasOwnProperty(k))
		console.log("  " + k + "  = " + vmap[k]);
if (isrec !== false) {
	console.log("recursion in elements:");
	console.log(isrec);
}

// make it recursive, then try again
subs['r'] = object;

vmap = {};
isrec = checkRecursive(object, vmap);
console.log("object (2) is " + (isrec === false ? "ok" : "recursive"));
for (var k in vmap)
	if (vmap.hasOwnProperty(k))
		console.log("  " + k + "  = " + vmap[k]);
if (isrec !== false) {
	console.log("recursion in elements:");
	console.log(isrec);
}

// make it doubly recursive, then try again
object['rProperty'] = object['aProperty'];

vmap = {};
isrec = checkRecursive(object, vmap);
console.log("object (2) is " + (isrec === false ? "ok" : "recursive"));
for (var k in vmap)
	if (vmap.hasOwnProperty(k))
		console.log("  " + k + "  = " + vmap[k]);
if (isrec !== false) {
	console.log("recursion in elements:");
	console.log(isrec);
}