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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: custom event in IE
Date: Wed, 11 Jan 2017 08:25:24 +0100
Organization: PointedEars Software (PES)
Lines: 45
Message-ID: <3041725.QJadu78ljV@PointedEars.de>
References: <ZpKdncuDJ6SUqenFnZ2dnUU7-YHNnZ2d@westnet.com.au> <8bydnVoLx8BUq-nFnZ2dnUU7-bednZ2d@westnet.com.au> <4259298.GXAFRqVoOG@PointedEars.de> <drGdnYqmpYpK_unFnZ2dnUU7-bfNnZ2d@westnet.com.au> <2568174.e9J7NaK4W3@PointedEars.de>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
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Xref: csiph.com comp.lang.javascript:32165

Thomas 'PointedEars' Lahn wrote:

> Because not only “new CustomEvent(theEvent)” may throw an exception, you 
> should not simply handle all exceptions caused by this statement with the 
> catch code, but only the specific one.  Since there is no compatible way 
> to catch only a specific type of exception (AFAIK only Mozilla JavaScript
> has a way, see the ES Matrix), you should rethrow the exception if it is
> not the one that you want to handle.  For example:
> 
>   try {
>     elem.dispatchEvent(new CustomEvent(theEvent));
>   } catch (err) {
>     if (!(err instanceof TypeError)) throw err;
> 
>     var evt = document.createEvent("CustomEvent");
>     evt.initCustomEvent(theEvent, true, false, {});
>     elem.dispatchEvent(evt);
>   }

Also, DRY:

  var evt = null;

  try {
    evt = new CustomEvent(eventType);
  } catch (err) {
    if (!(err instanceof TypeError)) throw err;

    evt = document.createEvent("CustomEvent");
    if (evt) evt.initCustomEvent(eventType, true, false, {});
  }

  if (evt) {
    try {
      elem.dispatchEvent(evt);
    } catch (e) {
      console.error(e);
    }
  }

-- 
PointedEars
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