functions & their own lexical environment

function foo() {
  return function inner() {
    console.log(bar);
  }
}
function outer() {
  var bar = 0;
  var fakeInner= foo();  

  // not the same as "var fakeInner= function () { console.log(bar); }"
  fakeInner();
}
outer(); // ReferenceError: bar is not defined 

Functions do only have access to their own lexical environment - from where they were defined. JavaScript does not have dynamic scope where a function has any kind of access to the scope where it is called.
This happens by attaching the scope to the function object, it is a part of the closure.

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