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Re: 'undefined' in declaration of function

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In comp.lang.javascript message <617c6390-5eea-43e2-881b-0fb60bb62e46@t3
5g2000yqd.googlegroups.com>, Tue, 29 May 2012 05:30:44, Scott Sauyet
<scott.sauyet@gmail.com> posted:

>One silly flaw in Javascript that would probably have been removed had
>the language not been standardized so quickly is that `undefined` is
>not a keyword like `null`.  It is simply a global property.  Arbitrary
>code can overwrite it.  So a library like jQuery that's operating in a
>very heterogeneous environment cannot assume that no other code has
>overwritten that property.  This is one way to restore it.  Inside the
>function, `undefined` is now pointing to the value of the second
>parameter passed to the function.  Since we don't pass a parameter
>there, the value is undefined, exactly what we want the `undefined`
>property to represent.  Note that this does *not* override the global
>property; it simply shadows it.  Outside this function, everything
>reverts to the way it was (except that any functions which close over
>`undefined` will also have the shadowing version [and if that doesn't
>make any sense to you, don't worry about it for now.])
>
>There are other ways this could be done, but this one is common, and I
>don't see any major flaws with it?  Other opinions?

The routine is then relying on something external to itself, its call.

I have used    var U    within the routine, with U on one side of  ==
or  !=  tests, with success;  possibly  ===  or  !==  tests would be
safer;  I don't generally use  U  for any other purpose when confusion
might occur.

-- 
 (c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk  Turnpike v6.05  MIME.
  Web  <http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms and links;
  Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
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'undefined' in declaration of function trunikov <dmitry.trunikov@gmail.com> - 2012-05-29 04:58 -0700
  Re: 'undefined' in declaration of function Scott Sauyet <scott.sauyet@gmail.com> - 2012-05-29 05:30 -0700
    Re: 'undefined' in declaration of function trunikov <dmitry.trunikov@gmail.com> - 2012-05-29 05:44 -0700
    Re: 'undefined' in declaration of function Dr J R Stockton <reply1222@merlyn.demon.co.uk.not.invalid> - 2012-05-30 20:06 +0100
      Re: 'undefined' in declaration of function Scott Sauyet <scott.sauyet@gmail.com> - 2012-05-31 05:22 -0700

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