[Javascript] Try and Catch Question

[MEM]

THANK A LOT for all the replys. :) I'm more then glad! 

Here I go digging deep into javascript again! :)

Thanks a million, really. Hope I can count on the mailing list for more
newbie questions, because I really want to properly LEARN javascript.
And one day maybe I will be on your side. 

Regards,
Márcio


-----Original Message-----
From: javascript-bounces at lists.evolt.org
[mailto:javascript-bounces at lists.evolt.org] On Behalf Of Troy III Ajnej
Sent: terça-feira, 3 de Março de 2009 15:44
To: javascript at lists.evolt.org
Subject: Re: [Javascript] Try and Catch Question


Hello MEM,

 

> Well, I have seen also with ‘err’ etc, so I presume the point is to have

> only something that represents the name error. But, what for? I mean,

> normally in this kind of statements I never see that ‘e’ or ‘err’ being
used

> for nothing, I see no e=”ups error” or something. So, what is that e for?

 

The "catch(whatever)" is obviously a function-call that depends on

the coder input for it to become useful. If you catch the error, you

are certainly aiming to get the cause, and since there was no way

of knowing the argument-name of this function for all the browsers

that wrote it independently, it was wisely decided to let this arg

be named by the coder so you can extract at least some poor laconic

info about the expected error using your own bite.

Anyway the catch() function will fail to execute if this arg is missing.

It will most probably yield "null", so the error will slip off the catch and

the suppression will fail.

 

> Why do we need the ‘e’ ?

Aside the fact that omitting "e" will cause the error capture to fail
suppress

the expected error, we need it to watch for our runtime errors like in:

 

try {

 thisUndeclaredFunction()

 }

 

catch(thatError){ 

 alert(thatError.message)

 }

 

[As you can see we're not using "e" or "err"]

 

In this example our alert(thatError.message) request will report:

"Object expected" or if we alert(thatError.name) we'll get "typeError"

meaning: error in expected variable type has occurred, which is caused

by "thisUndeclaredFunction()" name variable call.

 

It is completely unreasonable to call "document.getElementById()"

if you are not aiming to really catch some particular element in your var.

Therefore using the catch() method to simply suppress some error

you don't care to know what, might well be called a misuse, since

suppressing errors anonymously can be achieved globally by simply returning

"true" for the "onerror" event.

 

Regards.

 

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                      Troy III
                         progressive art enterprise
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 
> From: talofo at gmail.com
> To: javascript at lists.evolt.org
> Date: Mon, 2 Mar 2009 12:16:02 +0000
> Subject: [Javascript] Try and Catch Question
> 
> Hi all, this is my first post, (so if anything is not right in the way I
> post, please let me know).
> 
> 
> 
> 
> 
> When we use a try catch statement like this:
> 
> try {
> 
> 
> 
> } catch (e) {
> 
> 
> 
> }
> 
> 
> 
> Why do we need the ‘e’ ?
> 
> 
> 
> Well, I have seen also with ‘err’ etc, so I presume the point is to have
> only something that represents the name error. But, what for? I mean,
> normally in this kind of statements I never see that ‘e’ or ‘err’ being
used
> for nothing, I see no e=”ups error” or something. So, what is that e for?
> 
> 
> 
> 
> 
> Thanks a lot,
> 
> Márcio
> 
> _______________________________________________
> Javascript mailing list
> Javascript at lists.evolt.org
> http://lists.evolt.org/mailman/listinfo/javascript

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