Is there a way to say collection[attr1=value].attr2=value in Javascript?

Is there a way to say something like

User.friends[id=1].posts=data

in Javascript, where User.friends is a collection of Friend items, one of whose properties is 'id'?

I am iterating over a collection User.friends, which is a collection of Friend objects that have 3 properties (id, posts, and likes). The inner iterator instance variable, friend, seems passed-by-value not by-reference; so, how do I elegantly set the parent object's properties from within the iterator?

    async.each(User.friends, function(friend, cb) {
            var url="https://graph.facebook.com/"+friend.id.id+"/?fields=posts&since="+ moment(postFromDate).format('YYYY-MM-DD') + '&access_token=' + User.accessToken;
            request.get({
                url: url,
                json: true
                }, function (error, response, body) {
                    if (!error && response.statusCode == 200) {
                        console.log(body);
                        //I WANT TO SET THE ACTUAL User.friend[i].posts value, 
                        //but I do not know how to get the value of 'i'?
                        friend.posts=body.data; //this just sets local friend var                           
                        cb(null); 
                    } else {
                        console.log(error);
                        throw error;
                    }

            });  //...request.get
            }, function(error, result) {
                callback();
        }); //...async_each

Sorry if this is a dumb question. Any help really appreciated. I've tried:

_.findWhere(User.friends,{id: friend.id}).posts=body.data;

but this doesn't seem to work (I think it just sets a local value).