Javascript: Performance of 'closured' variables

Javascript: Performance of 'closured' variables

Is this:
function Con () {
var foo = 42;
this.foo = foo
}
more slow than this:
function Con () {
this.foo = 42;
}
On subsequent uses of the foo variable on an object returned by an
invocation of the 'Con'-constructor? Ie. does it hurt if the variable has
first been living in the closure of the constructor invocation?