JavaScript pubsub with Observer addon, the observer is also has fake array capability

ObserverPubSub.js

function ObserverPubSub(parent, key_of_myself) {
    this._topics = {};
    this.length = 0;
    this._subUid = -1;
    this._parent = parent;
    this._name = key_of_myself;
}
ObserverPubSub.prototype = {
    //pubsub
    on: function(topic, func, token) {
        var topics = this._topics;
        if (!topics[topic]) {
            topics[topic] = [];
        }
        if (arguments.length == 2) token = (++this._subUid).toString();
        topics[topic].push({
            token: token,
            func: func
        });
        return token;
    },
    emit: function(topic) {
        var topics = this._topics,
            args = arguments;
        if (!topics[topic]) {
            return false;
        }
        setTimeout(function() {
            var subscribers = topics[topic],
                len = subscribers ? subscribers.length : 0;
            while (len--) {
                subscribers[len].func.apply(this, args);
            }
        }, 0);
        return true;
    },
    unsub: function(token) {
        var topics = this._topics;
        for (var m in topics) {
            if (topics[m]) {
                for (var i = 0, j = topics[m].length; i < j; i++) {
                    if (topics[m][i].token === token) {
                        topics[m].splice(i, 1);
                        if (topics[m].length == 0) delete topics[m];
                        return token;
                    }
                }
            }
        }
        return false;
    },
    //observer
    emit_recursive: function() {
        this.emit.apply(this, arguments)
        if (this._parent) this._parent.emit.apply(this._parent, arguments)
    },
    add: function(k, v) {
        var objv = new ObserverPubSub(this, k);
        this[k] = objv;
        objv._set(v);
        this.emit('add', k, v);
        if (this._parent) this._parent.emit_recursive('childadd', this, this._name);
        return k;
    },
    push: function(v) {
        var k = this.length++;
        this.add(k, v);
        this.emit('length', this.length);
        return k;
    },
    _set: function(k, v) {
        var isnew = this[k] === undefined;
        if (arguments.length == 1) {
            v = k;
            k = '_value';
        }
        if (this[k] instanceof ObserverPubSub) return this[k].set(v);
        this[k] = v;
        this.emit('set', k, v);
        if (this._parent) this._parent.emit_recursive('childset', this, this._name);
        return isnew;
    },
    set: function(k, v) {
        if (!this._set.apply(this, arguments)) {
            this.emit('change', k, v);
            if (this._parent) this._parent.emit_recursive('childchange', this, this._name);
        }
    },
    get: function(k) {
        if (arguments.length == 0) return this['_value'];
        return this[k];
    },
    toArray: function() {
        var arr=[];
        for (var i = 0, j = this.length; i < j; i++) {
            arr[i]=this[i];
        }
        return arr;
    }
};

//var arr= new ObserverPubSub();
//pubsub:
//var token=arr.on('foo',function(){})//token='0'
//arr._topics
//arr.unsub('0')
//arr.on('set',function(eventname,key,value){console.log(eventname,key,value)})
//arr.on('add',function(eventname,key,value){console.log(eventname,key,value)})
//arr.on('change',function(eventname,key,value){console.log(eventname,key,value)})
//arr.on('length',function(eventname,key,value){console.log(eventname,key,value)})
//arr.on('childset',function(eventname,key,value){console.log(eventname,key,value)})
//arr.on('childadd',function(eventname,key,value){console.log(eventname,key,value)})
//arr.on('childchange',function(eventname,key,value){console.log(eventname,key,value)})
//observer:
//arr.add('key',"value");
//arr.set('key',"value");
//arr.push("value");//add with key=length,length++
//arr.get('key');
//arr.get(); // key='_value'
//arr.set("value"); // key='_value'