How do arrays store empty values - JavaScript

Not too long ago, I discovered that arrays in JavaScript need not contain an ordered set of keys (0-x) to store values within it

and some numeric keys may not be defined (0-4 ... 6-x, where 5 is not defined).

And this creates semantically two types of arrays that are similar:

arrayA = [, ,] (partially-empty arrays or sparse arrays)

arrayB = [undefined, undefined] (filled arrays)

But recently, I was tinkering with JavaScript in the Google Chrome Developer Console and came across this:

Now the second array is like arrayA, and the third like arrayB as shown in the console.

But the first array ([...'🏃🏽‍♀️'])... what is it?

I opened up its directory and saw the elements that were defined as hole were undefined with their respective keys in the array.

I also ran a few types of JavaScript loops on the array:

• for...in statement captures all elements, except the *hole*s.

• for...of statement captures all elements, except the *hole*s and proceeds to throw an error that the iterator variable used is undefined i.e.:

  for (var value of [...'🏃🏽‍♀️']) console.log(value);

  // Throw 'ReferenceError' when loop is done.

• Array.prototype.forEach method captures all elements, except the *hole*s.

• do...while, for and while statements captures all elements, except the *hole*s.

Why does the console see those values as different from empty or undefined (as with arrayA and arrayB)?

The main question is: Is there implicitly another type of array and if so, is there anything to note about it?