Javascript design patterns - child objects [on hold]

I am trying to improve the quality of my code by implementing design patterns. I've started reading JavaScript Patterns by Stoyan Stefanov, ive already read 1/3 of the book but dont see any mentioning about whether its a good practice for objects to have child objects. here's a quick example of what im talking about:

var Obj = {
    a : {
        str : "string",
        myFunc : function(){
            // some code here
        }
    }
}

I would appreciate some input on this