Code review - if else function

Question

I cannot for the life of me understand why I am getting the error:

"Type error: eCurVar is undefined". Please review the code below.

    var aBBTemplates = document.getElementsByClassName ("cBBTemplates");
    var i = 2;
    while (i < aBBTemplates.length)
    {
        var eCurVar = aBBTemplates[i];
        if (eCurVar === e.target)
        {
            eCurVar.style.zIndex = 3;
     // type error: eCurVar is undefined on the following line. 
        }   else if (eCurVar.style.zIndex === 3)    {
            console.log (eCurVar);
            eCurVar.style.zIndex = 3-1;
        }   else
        {
            console.log (eCurVar)
            eCurVar.style.zIndex = i;
        }
        i--;
    }

Bruno · Accepted Answer · 2018-04-28 04:07:31Z

3

After each iteration i is decremented of one unit... and after three iterations it becomes negative; so you read aBBTemplates[-1] you get undefined.

When you can't understand what's going on with few console.logs, your best bet is to add a debugger; instruction, and open your devtool (usually by pressing F12).

As for your problem you could fix it by adding a check on i:

while (i < aBBTemplates.length && i >= 0) {
}

edited Apr 28, 2018 at 4:07

answered Nov 21, 2012 at 10:26

Bruno

6,0006 gold badges36 silver badges54 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Kayote Over a year ago

Thank you, that made perfect sense.

Dennis Traub · Accepted Answer · 2012-11-21 10:25:17Z

1

In the second case aBBTemplates[i] probably returns null

answered Nov 21, 2012 at 10:25

Dennis Traub

51.9k7 gold badges100 silver badges113 bronze badges

4 Comments

Denys Séguret Over a year ago

Are you implying that getElementsByClassName returns an array containing null ?

Dennis Traub Over a year ago

I'm implying that aBBTemplates[i], i.e. the item of the array at index i, evaluates to null.

Dennis Traub Over a year ago

@dystroy If you read OP's code, you'll see that he's * decrementing* i and at some point it will be -1. And aBBTemplates[-1] probably will be null. Thanks for the downvote anyway.

Denys Séguret Over a year ago

I've read that, that's why I upvoted bru's answer, that is the first answer to bring something more than just repeating the error message. Seriously, I would have suggested to comment instead of answering if you had said more than that...

Jamiec · Accepted Answer · 2012-11-21 10:27:59Z

1

You start with i equal to 2. Lets assume that aBBTemplates[2] returns something meaningful. You do someting with it and them decrement i. Lets assume aBBTemplates[1] in meaningful.

Keep going, and sooner or lates i becomes -1, which will definately not be meaningful when reading aBBTemplates[-1]

answered Nov 21, 2012 at 10:27

Jamiec

136k15 gold badges143 silver badges202 bronze badges

Comments

Epsil0neR · Accepted Answer · 2012-11-21 10:28:39Z

1

Into if function check if also eCurrVar is not a null

if (eCurVar != null && eCurVar === e.target){
// your code
} else {
// if ecurvar == null or ecurvar != e.targer
}

Also in while check if your i is possitive number, because array do not contains items with negative indexes:

while(i >= 0 && i < aBBTemplates.length)

answered Nov 21, 2012 at 10:28

Epsil0neR

1,70416 silver badges25 bronze badges

Collectives™ on Stack Overflow

Code review - if else function

4 Answers 4

1 Comment

4 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

4 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related