Using an array to access (deeply) nested object properties

Question

Given javascript object:

obj = {
    a: {
        b: {
            c: 3
           }
       }
   }

I can access the deepest property as follows: obj['a']['b']['c'] or obj.a.b.c. Now I want to access this using an array ['a', 'b', 'c']. How can I access the same object property using this array?

Note: the method does not have to "safe", so no need to check for: typeError: cannot read property ... of undefined.

Yes, I can come up with a recursive solution but the problem seems so basic that I am afraid that I am missing something super obvious. (And I already need this as part of another recursive problem) — Roy Prins, Apr 24 '19 at 20:04

score 4 · Accepted Answer · edited Jul 04 '19 at 14:39

4

You can do this using reduce method and pass your object as accumulator param.

const obj = {
  a: {
    b: {
      c: 3
    }
  }
}

const key = ['a', 'b', 'c'];

function get(obj, key) {
  return key.reduce((r, e, i, a) => {
    return r[e] || (a[i + 1] ? {} : undefined)
  }, obj)
}

console.log(get(obj, key))

edited Jul 04 '19 at 14:39

Kobe

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answered Apr 24 '19 at 20:06

Nenad Vracar

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Sorry for the edit, I was just trying to test some code, meant to hit cancel not save :P – Kobe Jul 04 '19 at 14:39
@Kobe No worries it happens – Nenad Vracar Jul 04 '19 at 14:42
Im just trying to find away to access the object in this way but then also mutate that object, but I can't seem to get that to work. – Kobe Jul 04 '19 at 14:49
There are lots of different options based on your requirements how you want to set new value but you could start with something like this https://jsfiddle.net/syathrdg/3/, also take a look at lodash set method. – Nenad Vracar Jul 04 '19 at 15:01
Thank you so much, that's exactly what I needed. – Kobe Jul 04 '19 at 15:03
You're welcome. – Nenad Vracar Jul 04 '19 at 15:04

Using an array to access (deeply) nested object properties

1 Answers1