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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 04:09:22 +0100
Organization: PointedEars Software (PES)
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James Kirk wrote:

> Andrew Poulos <ap_prog@hotmail.com> wrote:
>> I used a try/catch and when it fails for IE the "catch" part uses
>> initCustomEvent
>> <https://msdn.microsoft.com/en-us/library/ff975987(v=vs.85).aspx>
>> to create the event:
> 
> I have always tried to avoid using try/catch. So just out of my own
> curiosity, why the try/catch over something liking to the function from:
> 
> [url]https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill[/url]

If the global object has no CustomEvent property in the MSHTML DOM, then 
such a polyfill would be a possibility.  If on the other hand it has such a 
property but the value of it just cannot be called a constructor, then the 
value would be a reference to a host object, and it would be unwise to try 
to overwrite the value.

> or testing in a similar fashion to that function.

You cannot determine whether a function can be called as a constructor 
unless you try it.

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