[Javascript] ending after for() in firefox

[Paul Novitski]

At 06:10 AM 3/6/2006, Michael Borchers wrote:
>this script works fine in IE, the alerts after the for() are shown
>and even the new lines are created, but firefox seems to stop
>right after the for() in countRows().
>
>what's wrong?


Michael,

Here's your bug:

HTML:
<input type="button" value="Optionen hinzuf&uuml;gen" 
onClick="addOptionsNumRows();" />
<input type="submit" name="insert" value="Speichern" />

JavaScript:
         if(inputFields[i].getAttribute("name").substring(0,8) == "options[")

The if-test assumes that every input field has a "name" attribute 
(your first button doesn't) and that the name will be at least 8 
characters ("insert" is only 6).

When your script reaches your first button (value="Optionen 
hinzuf&uuml;gen") it attempts to execute the substring() method on a 
non-existent string object and fails.

For more robust code, and for ease of debugging, I like to break up 
those long expressions into their component parts.  For one thing, it 
lets you insert alert() statements into incremental bits of logic to 
pinpoint exactly where your script fails.

for(i=0;i<numTag;i++)
{
         sName = inputFields[i].getAttribute("name");
                 if (sName) sName = sName.substring(0,8);
                 if (sName && sName == "options[")
                 {
                         ...
                 }
}

or:

         if (inputFields[i].getAttribute("name")
         && inputFields[i].getAttribute("name").length >= 8
         && inputFields[i].getAttribute("name").substring(0,8) == "options[")
         {
                 ...
         }

(I can't recall if the substring() method will abort JavaScript if 
operating on too short a string, but it doesn't hurt to play it safe 
if you're not sure.)

Regards,
Paul