Problem setting values in loop

Question

I've got som problem setting some values in my js-code. I've tried to figure out what the problem is but still can't find the issue in the code.

It's the mostN, mostE, mostW, mostS values I want to set.

The alert at the end of the code i "Undefined". Why? And How do I fix it? Thx!

var mostN,
mostE,
mostW,
mostS;

for (i = 1; i < opts.markers.length; i += 1) //loops 5 times
{
$geocoder.geocode(
{
    address: opts.markers[i].address},
    function (result, status)
    {
        if (status === google.maps.GeocoderStatus.OK)
        {
            var str = [result[0].geometry.location]; // "(42.456465, -48.74116)"
            var realString = str.toString();
            var stop = realString.length - 1;
            var real = realString.substring(1,stop); // "42.456465, -48.74116"

            var arr = real.split(", ");

            var lat = arr[0].toString(); // "42.456465"
            var lng = arr[1].toString(); // "-48.74116"

            if(mostN > lat) { mostN = lat; }
            if(mostE < lng) { mostE = lng; }
            if(mostW > lng) { mostW = lng; }
            if(mostS < lat) { mostS = lat; }

            alert(mostN); // returns "Undefined"
        }
        else
        {
            if (opts.log) {console.log("Geocode was not successful for the following reason: " + status); }
        }
    }
);

}

Do you ever actually set mostN to anything at all? It's not clear from this code that you do, which would explain why it's undefined. — Jeff
– Jeff, Commented May 23, 2011 at 6:34
@Awais well, not only in php variable can have name '$geocoder'. — pabdulin
– pabdulin, Commented May 23, 2011 at 6:36

RobG · Accepted Answer · 2011-05-23 07:34:41Z

You don't seem to be taking into account the sign of the lat and long. For example,

> var mostN, 
> ...
> var lat = arr[0].toString(); // "42.456465"

From your post, lat is already a string so converting it to string seems pointless. Given that later an arithmetic comparison is performed, it would be better to convert it to number up front:

var lat = Number(arr[0]); // 42.456465

or

var lat = +(arr[0]); // 42.456465

.

>  ...
>     if(mostN > lat) { mostN = lat; }
>     if(mostE < lng) { mostE = lng; }
>     if(mostW > lng) { mostW = lng; }
>     if(mostS < lat) { mostS = lat; }

The variable mostN has not been initialised so in the comparison it is equivalent to zero, which is not greater than 42.456465, so the test returns false and mostN is not set. However, mostS will be set.

But the sign of the comparison is wrong - if the latitude is a bigger +ve number it is more northerly so:

    if (mostN < lat) { mostN = lat; }

is what you want, same for the rest of the tests. However, you also have to take into account the hemisphere where -10 is more northerly than -20, so (provided mostN and lat are numbers, not strings):

    if ((mostN + 90) < (lat + 90)) { mostN = lat; }

since latitude is never greater than 90 degrees. For longitude, use 180. You can use any number you like that is 90 or greater for lat and 180 or greater for long, so you could use 180 for both but that might be confusing for maintainers.

sje397 · Accepted Answer · 2011-05-23 06:48:54Z

1

Try something like:

var SOMETHING_HUGE = 100000000;
var mostN = -SOMETHING_HUGE,
mostE = -SOMETHING_HUGE,
mostW = SOMETHING_HUGE,
mostS = SOMETHING_HUGE;

//...

if(lat > mostN) { mostN = lat; }
if(lng > mostE) { mostE = lng; }
if(lng < mostW) { mostW = lng; }
if(lat < mostS) { mostS = lat; }

edited May 23, 2011 at 6:48

answered May 23, 2011 at 6:35

sje397

41.9k9 gold badges90 silver badges106 bronze badges

2 Comments

Jeff Over a year ago

I think you reversed some of the operands?

sje397 Over a year ago

@Jeff - I'm using the +N, +E convention there :)

pabdulin · Accepted Answer · 2011-05-23 06:34:17Z

0

Works as it should, since at the moment of check variable mostN is undefined, and condition mostN > lat is false.

answered May 23, 2011 at 6:34

pabdulin

35.6k9 gold badges66 silver badges102 bronze badges

1 Comment

RobG Over a year ago

It might "work" in that it produces the results the code defines, but it is logically wrong because not only are the comparisons backwards, but it doesn't allow for consider hemispheres.

Muhammad Zeeshan · Accepted Answer · 2011-05-23 06:37:43Z

0

Your mostN is not clearly initialize with some value.Try to place alert inside

if(mostN > lat) { mostN = lat; }

condition. And also check the if comparison is correct or not.

answered May 23, 2011 at 6:37

Muhammad Zeeshan

8,86610 gold badges47 silver badges55 bronze badges

Collectives™ on Stack Overflow

Problem setting values in loop

4 Answers 4

1 Comment

2 Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

2 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related