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Re: Referencing an object prop with a string

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Michael Haufe (TNO) wrote:

> On Monday, February 1, 2021 at 9:07:06 PM UTC-6, Thomas 'PointedEars' Lahn
> wrote:
>> Michael Haufe (TNO) wrote:
>> > let walk = (o, path)=>path.split('.').reduce((o,k)=>o && o[k], o);
>> This does not work if the property name contains `.'. The approach to use
>> Array.prototype.reduce() is an elegant one, though, and can be applied to
>> supporting a path array (too), which solves that problem:
>> 
>> let walk = (o, path) => path.reduce((o, k) => o && o[k], o);
> 
> I wonder if a variant of JSONPath could be promoted into the language
> proper.

Yes, I am not particularly fond of Stefan Goessners syntax choices either.
While I could perhaps live with “@” instead of “.”, coming from the command 
shell I find “..” to access *subordered* items very counter-intuitive (I 
also did with E4X).  Why did he not propose and implement the familiar XPath 
syntax?  For example, I see no good reason to propose ”$” instead of “/”.

> I tried in the early ES5 days to convince the committee but there
> were bigger fish to fry at the time.

ACK.
 
> With Symbols and the spread operator, it may be harder to get a proposal
> through.

What exactly do you mean?

One problem I see is that there is not really a need for it anymore (or is 
there?): You can write now (and at least *execute* much more efficiently)

  obj?.store?.book?.filter((book) => book.price < 10)
    .map((book) => book.title) || []

instead of

  jsonPath(obj, '$.store.book[?(@.price < 10)].title')

Which reminds me of LINQ which solves similar problems. 
 
> At least Slice Notation has a change of succeeding:
> 
> <https://github.com/tc39/proposal-slice-notation>

Yes, I think that would be a useful and unproblematic addition.

I would even like a[-1] as in Python (seriously, is there a use-case for 
properties named named “-1” in an *array*?).  I added support for using 
negative indexes to access elements from the end of an array in 
JSX:array.js:BigArray with Proxy, and BigArray.prototype.get() to do it
in a backwards-compatible way, about 5 years ago:

<https://github.com/PointedEars/JSX/blob/e6eb05cb945df7b7304d572ccbac90ae9a632286/array.js#L491-L1158>

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | <http://PointedEars.de/es-matrix>
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | Please do not cc me./Bitte keine Kopien per E-Mail.

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Thread

Referencing an object prop with a string Andrew Poulos <ap_prog@hotmail.com> - 2021-01-31 14:42 +1100
  Re: Referencing an object prop with a string "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-01-30 19:52 -0800
    Re: Referencing an object prop with a string "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-01-30 19:54 -0800
    Re: Referencing an object prop with a string Andrew Poulos <ap_prog@hotmail.com> - 2021-01-31 20:29 +1100
      Re: Referencing an object prop with a string H e <he12457@hotmail.com> - 2021-01-31 02:17 -0800
    Re: Referencing an object prop with a string Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2021-02-02 04:06 +0100
      Re: Referencing an object prop with a string "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-02-02 13:01 -0800
        Re: Referencing an object prop with a string Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2021-02-02 23:50 +0100
          Re: Referencing an object prop with a string "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-02-02 19:19 -0800
            Re: Referencing an object prop with a string "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2021-02-02 19:26 -0800
            Re: Referencing an object prop with a string Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2021-02-03 19:42 +0100

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