JS: How can I prevent access to the global variables do?

Question

Is to disable the global variable in the function that I want.

I would make like Expenssion of Adobe After Effect

example code :

function privateFunction(){
    return window;
}

then normally :

result : Window Object

but I want then :

result : undefined

What should I do?

please help me

I want blocking global variable access in function;

Answer 1

Shadow the global variable by a local one:

function privateFunction() {
    var window;
    return window; // not the Window, but undefined now
}

Answer 2

You need to wrap everything in a closure:

    (function() {
        var window = 'foo';
        function privateFunction(){
            return window;
        }
    
        console.log(privateFunction());
    })();