Adding keys to a json using an array of string

Question

I have a basic json question that is giving me headache since a couple of hours, I am trying to dynamically add keys to a Json object using an array of string.

Here is my array of string:

let key =  ['session', 'view_state', 'footer', 'config', 'items']

I have another variable which is jsonValue and is my whole json object. I want to end up with one of those options:

jsonValue.session.view_state.footer.config.items
jsonValue['session']['view_state']['footer']['config']['items']

This is my best attempt using a forEach.

forEach(jsonKeys, (el) => {
  jsonCollection += jsonCollection !== undefined ? '."' +[el + '"'] : [ '"' + el + '"' ];
})

But I have this result:

undefined"session"."view_state"."footer"."config"."items"

Any help will be appreciated!

What is the end result you are after? How will you use this object stricture? Do you want jsonValue.session.view_state.footer.config.items to be a specific value? an object, an Array, something else?? Or are you trying to pass in the array to get at a specific value from your object? — Intervalia
– Intervalia, Commented Nov 21, 2017 at 22:32
I am trying to pass the array to get a specific value from my Json object, yes. Whether it is a string on another array — Jean-Baptiste
– Jean-Baptiste, Commented Nov 21, 2017 at 22:41

Ori Drori · Accepted Answer · 2017-11-21 23:00:42Z

3

To get a value using the keys array

Iterate with Array#reduce, check the type of the current value, if it's an object, return the value of the key, if not return undefined:

const obj = {
  "demo": true,
  "session": {
    "view_state": {
      "footer": {
        "config": {
          "items": [
            1,
            2
          ]
        }
      }
    }
  }
};

const keys =  ['session', 'view_state', 'footer', 'config', 'items'];

const value = keys.reduce((val, key) => val && typeof val === 'object' ?
  val[key] : undefind, obj);

console.log(value);

To add a value using the keys array

Use Array#reduceRight to create a chain of objects with the value you want. Use Object#assign to update the original object with the results:

const keys =  ['session', 'view_state', 'footer', 'config', 'items'];

const obj = { demo: true };

Object.assign(obj, keys.reduceRight((val, key) => ({ [key]: val }), [1, 2])); // replace [1, 2] with the actual items

console.log(obj);

edited Nov 21, 2017 at 23:00

answered Nov 21, 2017 at 22:24

Ori Drori

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3 Comments

Forty3 Over a year ago

Wow, Array#reduceRight .. what a fascinating bit of code. Nice answer!

Marouen Mhiri Over a year ago

very elegant solution ;-)

Jean-Baptiste Over a year ago

Short and neat! Thank you

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