understanding the javascript global namespace and closures

Is there a god (i.e. a parent) object?

Yes. More technically, it’s the global object that all these primitives are members of; it just happens that in the browser, the window object is the global object.

> window.String === String;
true

Why is it bad idea to have vars/functions on a global level?

Because if you’re adding lots of 3rd party libraries/ scripts, they all share the same global object, there’s the chance of name collisions. This is a real life problem with all the libraries which use $ as an alias (jQuery, Prototype and more).

If it is really a bad idea to have vars/functions in global scope then would closures be the best way to avoid this?

x shouldn’t be considered global. It’s part of the closure formed by declaring the child functions inside the parent() function. The problem part of your snippet is that parent() is global; what happens if some other code re-declared parent()? This would be better:

(function () {

function parent(){
    var x = 'some value';
    function child1(){
        x.someMethod()
    } 
    function child2(){
        x*something;
    }
    function child3(){
        x+=something;
        child2()
        child1()
    }
    child3()
}
parent()

}());

The fact x is accessible within the child functions isn’t bad; you should have written those functions yourself, so you should be aware of the existence of x. Bear in mind that if you re-declare x within those child functions with var, you won’t affect the x in parent().