为什么这种模式会泄漏内存

Question

以下是我所拥有的一些代码的非常简化（有点难看）的版本。当我在代码执行之前和之后比较Chrome中的堆snapsnots时，不会收集someObject和subObjectCollection。这让我感到困惑，因为看起来泄漏是由循环引用引起的，这对于Chrome中的v8垃圾收集器来说应该不是问题。我没看到这个导致它泄漏的代码？如何重构以便清理这些对象？ JSFiddle

var someObject = function (name) {
    var _subObjects = [];
    this.name = name;
    var parent;

    this.getObjects = function () {
        return _subObjects;
    }

    this.addObject = function (o) {
        _subObjects[_subObjects.length] = o;
        o.setParent(this);
    }

    this.setParent = function (o) {
        parent = o;
    }

    this.getParent = function () {
        return parent;
    }
}

var subObjectCollection = function (name) {
    var parent;
    this.name = name;
    this.list = [];


    this.setParent = function (o) {
        parent = o;
    }

    this.getParent = function () {
        return parent;
    }
}

var obj1 = new someObject("Top Level Object");
var objCollection = new subObjectCollection("Object Collection");
obj1.addObject(objCollection);
var obj2 = new someObject("Child Object");
obj2.setParent(obj1);
obj1.getObjects()[0].list[0] = obj2;