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From: James Kirk <noneya.invalid@gmail.com>
Newsgroups: comp.lang.javascript
Subject: Re: check for obj nested prop
Date: Fri, 8 May 2020 11:00:12 -0400
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In Message: <C9udnTlJHfCQbSnDnZ2dnUU7-U3NnZ2d@westnet.com.au>
Andrew Poulos <ap_prog@hotmail.com> 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?

nested destructuring

let objA = {big: 'toe'},
objB = {A: {B: {C: {D: 'look at D' } } } },
{a,a:{b,b:{c,c:{d}=''}=''}=''} = objA,
{A,A:{B,B:{C,C:{D}=''}=''}=''} = objB;

console.log(a);
console.log(b);
console.log(c);
console.log(d);

console.log(A);
console.log(B);
console.log(C);
console.log(D);

-- 
James Kirk