sequence of code inside function changed (?)

Is there a reason for allowing such deviant syntax?

I often wonder that about a lot of JS :)

function a() {
  function foo() { return "All is well with the world..." }
  return foo();
  function foo() { return "Oh God no. This is horrible!" }
}

function b() {
  var foo = function() { return "All is well with the world..." }
  return foo();
  foo = function() { return "Oh God no. This is horrible!" }
}

a(); // "Oh God no. This is horrible!"
b(); // "All is well with the world..."

I think it was a side-effect of turning it into Bytecode first as @allObjects says, but then they thought it was handy so they left it in...

At some point I will implement this properly, there are some nice side-effects when applied to Espruino:

function a() {
  function b() {
    // ...
  }
  setTimeout(b,500);
}

The code above would have had the function b parsed beforehand, so execution would be faster, and if you called it twice it'd be able to use the same copy of b's code, saving memory.