josh99 - pastebin.com/2fbiMMxM

gistfile1.js

var age, foo;
age = 99;
foo = function() {
  return age = 0;
};

foo();
console.log(age); # => 0

------------------------

var age, foo;
foo = function() {
  var age;
  return age = 0;
};
age = 99;

foo();
console.log(age); # => 99