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Re: Best way to feature-test?

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Gregor Kofler wrote:

> Am 2012-07-16 02:50, perryv@gmail.com meinte:
>> […] lately, I've been reading that "document", "window" and other browser
>> objects are "host objects", and host objects have their own rules and
>> behaviors that depend on the browser and the platform. So it's possible
>> that merely testing "document.someFunctionality" can throw an exception
>> in some browser on some platform.
>>
>> So, in order to cover those cases, is it reasonable to do the following?
>>
>> if(typeof document.someProperty != 'undefined') {
>>      // Go ahead and use the property
>> }
>>
>> if(typeof document.someFunction == 'function') {
>>      // Go ahead and invoke "document.someFunction()"
>> }
>>
>> Or is it overkill?
> 
> Quite the contrary.
> 
> Some links for further reading:
> 
> <http://www.cinsoft.net/host.html>
> […]

I have since realized not only the usefulness of having a method that can 
deal with separate object reference and property names instead of a `typeof' 
result (isMethod), but also of having a separate method for methods of 
host and native objects (isNativeMethod) each. (jsx.object.isMethodType(), 
formerly isMethodType(), is still supported but has been marked deprecated 
accordingly.  It may not be supported in future revisions.)

Therefore, JSX:object.js contains jsx.object.isMethod()) (formerly 
isMethod()) since at least revision 123 (2008-05-29), and 
jsx.object.isHostMethod() (alias for .isMethod()) and 
jsx.object.isNativeMethod() (wrapper for .isMethod()) since revision 234 
(2011-12-12).  

jsx.object.areNativeMethods(), jsx.object.areHostMethods(), and 
jsx.object.areMethods(), the latter of which has been been introduced in 
revision 146 (2009-07-16), are aliases for those methods, respectively.  As 
an extension to the methods in David's library (so to speak), they also 
support calls of the form

  if (jsx.object.isHostMethod(window, "document", "write"))

(accepts an arbitrary number of arguments) which prevents you from having to 
write

  if (typeof window.document != "undefined"
      && jsx.object.isHostMethod(window.document, "write"))

and

  if (jsx.object.areHostMethods(document, ["open", "write", "close"]))

which prevents you from having to write

  var _isHostMethod = jsx.object.isHostMethod;
  if (_isHostMethod(document, "open")
      && _isHostMethod(document, "write")
      && _isHostMethod(document, "close"))

which is not only tedious to write but also inefficient by comparison.

See 
<http://PointedEars.de/websvn/filedetails.php?repname=JSX&path=%2Ftrunk%2Fobject.js> 
for more.


PointedEars
-- 
> If you get a bunch of authors […] that state the same "best practices"
> in any programming language, then you can bet who is wrong or right...
Not with javascript. Nonsense propagates like wildfire in this field.
  -- Richard Cornford, comp.lang.javascript, 2011-11-14

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Thread

Best way to feature-test? perryv@gmail.com - 2012-07-15 17:50 -0700
  Re: Best way to feature-test? perryv@gmail.com - 2012-07-15 17:54 -0700
  Re: Best way to feature-test? Gregor Kofler <usenet@gregorkofler.com> - 2012-07-16 10:48 +0200
    Re: Best way to feature-test? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-07-16 21:29 +0200
  Re: Best way to feature-test? Ivan The Not-So-Bad <1suf41n@yahoo.com> - 2012-07-16 13:49 +0000
    Re: Best way to feature-test? Tim Down <timdown@gmail.com> - 2012-07-16 08:42 -0700
      Re: Best way to feature-test? Ivan The Not-So-Bad <1suf41n@yahoo.com> - 2012-07-16 17:35 +0000
  Re: Best way to feature-test? Jim T. <x@y.z> - 2012-07-18 13:22 -0400
    Re: Best way to feature-test? Jim T. <x@y.z> - 2012-07-18 13:24 -0400

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