What is happening in this loop?

[jpvargas10]

In one of the challenges it asks to use a while loop to fill an array of descending numbers. I know I can just use an ascending loop and unshift but this was my initial plan and I’m getting errors I don’t understand.

// Setup

var myArray = [x];

// Only change code below this line

var b = 6;

while(b > 0){

  myArray.push(b);

  b--;

  console.log(myArray[b]);

}

Output:
undefined
undefined
undefined
4
5
6

Like I understand if I get the wrong range of numbers or one of them is undefined because while loops do an extra iteration but why so many undefined?

[JeremyLT]

@jpvargas10

myArray[b]

What exactly is this?

[kevinSmith]

I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.

See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (’).

[kevinSmith]

@jpvargas10

var myArray = [x];

And what is this? Is x defined somewhere else?

[jpvargas10]

Sorry first time using forum.

X should not be there. It’s the setup for the challenge and I’m not supposed to change it, it’s an empty array.

var myArray = [];

[kevinSmith]

OK, then we are back to Jeremy’s idea. What if you did:

console.log(myArray);

We don’t think that that b represents what you think it does.

[jpvargas10]

YES thank you so much. This helped me see it better. I was outputting the index not the array itself so of course the index of an array that it doesn’t have would be undefined.

[jpvargas10]

var b = 5;

while(b > -1){

  myArray.push(b);

  b--;

  console.log(myArray);

}