JS scope/hoisting quiz

gistfile1.js

// Without cheating by running the code,
// what do these 3 result in?

function foo(a) {
   a();
   function a() {
      console.log("yay");
   }
}

foo(); // ??
foo( undefined ); // ??
foo( function(){ console.log("bam"); } ); // ??

1. foo(); //yay
2. foo( undefined ); //yay
3. foo( function () { console.log("bam"); } ); //yay

Could you please explain why ?

-This might sound weird but javascript is considering variable a to be "function" because it is defined as such in foo's function declaration.
-Now as to why function a() is able to return the output of console.log even though it is called before it is declared in function foo() is due to the fact that the JavaScript interpreter "looks ahead" to find all the declarations (it's called function hoisting. Check this link to know more:
http://adripofjavascript.com/blog/drips/variable-and-function-hoisting.html)

This is a nightmare.

yay
yay
yay

what happened is like the folllowing:

function foo(a) {
  a = function() {
    console.log('yay')
  }
   a();
}

yay

yay
yay
yay