Question

Are variables defined inside an inner function that have the same name as a variable in an outer function isolated from the outer variable?

function() {
    var myTest = "hi there";
    ( function( myTest ) {
        myTest = "goodbye!";
    } )();
    console.log( myTest ); // myTest should still be "hi there" here, correct?
}

Naturally if I didn’t declare myTest inside the inner function it would create a closure and modify the original. I just want to make sure that variables declared within an inner function are always isolated to that function even if their name may conflict with an outer scope.

Answer 1

Yes, they effectively do. Each function creates a new scope, and the closest scope in which a requested variable is declared always takes precedence. No exceptions.