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Message-ID: <2017556.lXCzD688iH@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Tue, 29 May 2012 17:40:08 +0200
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Subject: Re: When is onclick *not* triggered?
Newsgroups: comp.lang.javascript
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Xref: csiph.com comp.lang.javascript:14209

Tim Slattery wrote:

> We have a legacy app that uses a somewhat odd method of submitting a
> page, and it's giving us fits.
> 
> There's no "<input type='submit'...> button on the page. What is there
> is an image of a "Continue" arrow surrounded in an <a ... > tag. Here
> it is:
> 
>    <a href="" onclick="submit_page(contactForm, 'prices');return
> false;"
>       title="Continue through the Web site" scope="request" >
>          <img border="0" src="/GlobalContent/images/arrowContinue.gif"
> align="middle"/>
>    </a>

And invalid markup on top of that.  I have seen such nonsense before in my 
job as well.

> The "submit_page" script sets a couple of values and submits the form
> Works just fine,  nearly always.

See below.

> The problem is that in a very few cases, it looks like the href tag is
> activated (for lack of a better term)

The better (and correct) wording would be "the `A' element is activated".  
`href' is not a tag, it is an attribute (name).

> without triggering the onclick.

Unlikely, but possible.

> The result is that the page is submitted to a nonexistent address.

Incorrect.  `""' is a same-document reference.  As a result, there is a race 
condition if the `click' event is not canceled (which is short for "the 
default action of the `click' event is not prevented", see 
preventDefault()).
 
> So my question is how could this happen?

Client-side scripting is not supported or the submit_page() call throws an 
exception.  You do not handle that exception, which is why the program 
aborts.  If it aborts, usually the `onclick' attribute value is processed as 
if it was not there.

> The errors seem to be reported by people using IE8. I've run my tests
> with that browser and haven't turned up anything.

The nature of a race condition is that it is not reproducible or hard to 
reproduce.  Replace the legacy approach, and fix your function, so that 
there is no race condition.


PointedEars
-- 
Sometimes, what you learn is wrong. If those wrong ideas are close to the 
root of the knowledge tree you build on a particular subject, pruning the 
bad branches can sometimes cause the whole tree to collapse.
  -- Mike Duffy in cljs, <news:Xns9FB6521286DB8invalidcom@94.75.214.39>