Variable scoping gotchas

Phil points to this great bit by Scott Issacs about JavaScript variable scoping. I've seen hardcore programmers as well as JS newbies make the same simple mistake:

function Foo() {
  bar = 1;
}

You might assume bar is private to Foo, but you'd be mistaken. Variables declared without the var operator are global by default. The correct syntax is:

function Foo() {
  var bar = 1;
}

Check out Scott's weblog for more scripty goodness.