What's wrong with my logic? (JS string Length)

Question

A couple days ago, on a site that I'm the only author on, I added this code to a script:

if (PowerArray[0][0].length < 1);
{
    return false;
}

and everything worked fine. When PowerArray[0][0] was "70", the script ran. When PowerArray was empty, the script didn't run past the above quoted line. This is no longer true. For the life of me, I can't figure it out. I tested with variants of the code, like below:

if (PowerArray[0][0].length < 1);
{
    alert(PowerArray[0][0].length);
    return false;
}

and set PowerArray[0][0] = "70". When I run the code, I get an alert with "2" in the text. This is the only place that I have an alert in the script. What's going on here, and how do I fix it?

Note: The expected behavior is, of course, no alert, because "70" has a length of 2, and shouldn't trigger the truth of the if.

Edit: 1) Yes, the False in the first block was a typo. It's been corrected. 2) The expected behavior was for it to stop processing if (and only if) PowerArray[0][0].length was 0. 3) I had previously initialized PowerArray as an empty array, and then copied an array (which had the potential to be empty) into it.

You have some semicolons at the end of your `if` statements which might be causing issues. — Tom A, Jul 16 '13 at 04:43
I've not checked, but I'm fairly certain `False` shouldn't work at all. Typo? — David Thomas, Jul 16 '13 at 04:44

Rails Guy · Accepted Answer · 2013-07-16T06:13:20.983

4

You should remove semicolon from if statement, it terminates your statement there. And yes, when your PowerArray is empty, PowerArray[0][0] will throw an undefined error, So should put a null check for that as well.

edited Jul 16 '13 at 06:13

answered Jul 16 '13 at 04:46

Rails Guy

3,836
1
20
18

it is a logical error, but not the reason for the later scripts not running when `PowerArray ` is empty – Arun P Johny Jul 16 '13 at 04:49
@ArunPJohny but it is why the asker is observing 70 in his array. Upvoting your answer, however, because that's the next issue OP will encounter. – John Dvorak Jul 16 '13 at 04:50

Arun P Johny · Answer 2 · 2013-07-16T04:59:45.800

3

when PowerArray is empty PowerArray[0] gives undefined then you will get an error for PowerArray[0][0] saying TypeError: Cannot read property '0' of undefined that is why the script is nor running after that line

if (PowerArray && PowerArray[0] && PowerArray[0][0] && PowerArray[0][0].length < 1)
{
    return false;
}

edited Jul 16 '13 at 04:59

answered Jul 16 '13 at 04:46

Arun P Johny

384,651
66
527
531

Still has a syntax error, because `False` is not a valid Javascript keyword. Unless I'm missing something... And you missed the trailing semicolon... – beatgammit Jul 16 '13 at 04:52
@tjameson missed it totally – Arun P Johny Jul 16 '13 at 04:53

iJade · Answer 3 · 2013-07-16T04:55:02.273

0

try this

   if (PowerArray[0]) {
            if (PowerArray[0][0].length < 1) {
                return False;
            }
        }

edited Jul 16 '13 at 04:55

answered Jul 16 '13 at 04:45

iJade

23,144
56
154
243

apart from the extra semicolon you didn't fix... if the value is falsy, its length (if it has any) would be zero. – John Dvorak Jul 16 '13 at 04:49

score 0 · Answer 4 · edited May 23 '17 at 12:05

0

I think the semicolon after the if is the issue. I would also check if PowerArray is a valid 2D array implementation. Check this link for ideas How can I create a two dimensional array in JavaScript?

Start by changing it to this if (PowerArray[0][0].length < 1)

edited May 23 '17 at 12:05

Community

1
1

answered Jul 16 '13 at 04:46

TGH

38,769
12
102
135

What's wrong with my logic? (JS string Length)

4 Answers4