B.3.3.js

var p = () => console.log(f);
{
  p(); // undefined
  console.log(f); // function f(){}

  f = 1;
  
  p(); // undefined
  console.log(f); // 1
  
  function f(){}
  
  p(); // 1
  console.log(f); // 1

  f = 2;

  p(); // 1
  console.log(f); // 2
}

I should mention that this is just a compatibility hack in the specification, since block-scoped function declarations were not previously a part of the ECMAScript spec but were commonly supported with inconsistent semantics in browsers. These semantics are only intended to capture behavior which would have worked across browsers, to avoid breaking things which previously worked everywhere; it's not intended to be sensible.

Don't write sloppy-mode code and you won't need to worry about it.