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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: check for obj nested prop
Date: Sat, 09 May 2020 00:19:15 +0200
Organization: PointedEars Software (PES)
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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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