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Groups > comp.lang.javascript > #38391

Re: check for obj nested prop

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Andrew Poulos wrote:

> If I have an object and it get properties added dynamically when I need
> to test for a "nested" property and one of the "ascendant" properties
> doesn't exist I get an error. For example,
> 
> let obj = {a: 1};
> if (a.b.c.d) // throws error
> 
> so I end up doing
> 
> if (a && a.b && a.b.c && a.b.c.d)
> 
> What happens is that every now and then I get caught when I assume the
> properties should exist.
> 
> Is there a way to get the check value of an object's nested property
> without first having to test for all the ascendant properties?

No.  Therefore I had written jsx.object.getFeature().  It has the advantage 
over the approach presented by “JJ” that it also supports property names 
that contain a “.”.  It basically differs from their approach in that you 
(can) pass multiple String values as arguments instead of a single String 
value.  (I had the one-string approach first, but ran into problems with “.” 
in property names.)

It can be used like this:

  if (_getFeature(a, 'b', 'c', 'd')) {
    // …
  }

<https://github.com/PointedEars/JSX/blob/master/object.js#L970>

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check for obj nested prop Andrew Poulos <ap_prog@hotmail.com> - 2020-05-08 15:37 +1000
  Re: check for obj nested prop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-05-08 10:52 +0100
    Re: check for obj nested prop Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2020-05-09 00:26 +0200
      Re: check for obj nested prop Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-05-09 03:09 +0100
        Re: check for obj nested prop Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2020-05-12 09:28 +0200
          Re: check for obj nested prop Julio Di Egidio <julio@diegidio.name> - 2020-05-12 04:01 -0700
    Exception handling (was: check for obj nested prop) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2020-05-09 03:46 +0200
  Re: check for obj nested prop JJ <jj4public@vfemail.net> - 2020-05-08 17:18 +0700
  Re: check for obj nested prop Julio Di Egidio <julio@diegidio.name> - 2020-05-08 03:53 -0700
  Re: check for obj nested prop James Kirk <noneya.invalid@gmail.com> - 2020-05-08 11:00 -0400
  Re: check for obj nested prop Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2020-05-09 00:19 +0200
    Re: check for obj nested prop Julio Di Egidio <julio@diegidio.name> - 2020-05-12 04:04 -0700
      Re: check for obj nested prop luserdroog <luser.droog@gmail.com> - 2020-05-12 07:59 -0700
  Re: check for obj nested prop "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2020-05-12 14:17 -0700
    Re: check for obj nested prop Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2020-05-13 02:46 +0200
    Re: check for obj nested prop Andrew Poulos <ap_prog@hotmail.com> - 2020-05-13 13:08 +1000
      Re: check for obj nested prop "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2020-05-13 12:30 -0700

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