Programmatically traverse JavaScript object and replace part of it

Question

let tObj = {
     "name" : "testName",
     "location" : {
        "name": "nextLevelName",
        "address" : {
            "street" : "deep street"
        }
    }
}

let id = "location-address-street";
let newValue = "another deep street";

In the JavaScript object above I'd like to replace the street. I want this to be done by a function that can replace any value in any object given an object and the id string which contains the unique keys separated by "-" that lead to the property which value needs to be replaced. I am thinking that initially one would list the keys of the first object "level", then check if any of those keys is in the id string, if so move to the next level, etc. (kind of screams for recursion?)

"initially one would list the keys of the first object "level", then check if any of those keys is in the id string" - no. Just look at the first name in the path, and check whether it exists in the object. Do not enumerate all keys of the object. "then move to the next level, kind of screams for recursion?" - yes. — Bergi
– Bergi, Commented Jul 24, 2022 at 14:05

Tachibana Shin · Accepted Answer · 2022-07-24 13:44:36Z

1


const keysDeep = id.split("-")

keysDeep.slice(0, -1).reduce((obj, key) => {
  if (!(key in obj)) return obj[key] = {}

  return obj[key]
}, tObj)

[keysDeep[keysDeep.length -1]] = newVal

answered Jul 24, 2022 at 13:44

Tachibana Shin

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3 Comments

Bergi Over a year ago

@KimSkogsmo That doesn't create "missing" objects like the answer does

Bergi Over a year ago

Btw to really save bytes, write (o,k)=>o[k]??={}

Kim Skogsmo Over a year ago

@Bergi Oh, damn, I didn't see the assignment, read that too fast :P Nice fix.

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