Recursive data in JSON object

Question

{
"groups": [
    {
        "name": "Event",
        "groups": [
            {
                "name": "Service",
                "subscriptions": [
                    {
                        "topic": "SERVICE_STATUS_PRESETS"
                    },
                    {
                        "topic": "AIRCRAFT_ACTIVATION",

                    },
                    {
                        "topic": "OUT_OF_SERVICE",

                    }
                ]
            }
        ]
    },
    {
        "name": "Enquiries",
        "groups": [
            {
                "name": "Service-related",
                "subscriptions": [
                    {

                        "topic": "PROMO_CODES_REQUESTS",

                    }
                ]
            }
        ]
    }
],
"subscriptions": [
    {
        "topic": "BANNERS",
    },
    {
        "topic": "DOCUMENTS",
    },
    {
        "topic": "USER",
    }
]

}

OK guys I have such JSON structure what I need is to: return all topics in array, in this example it will be:

["SERVICE_STATUS_PRESETS", "AIRCRAFT_ACTIVATION", "OUT_OF_SERVICE", "PROMO_CODES_REQUESTS", "BANNERS", "DOCUMENTS", "USER"]

I try recursive calls like this, though I only get last three records:

getRecursive() {
if (Array.isArray(data)) {
       for (let i = 0; i < data.length; i++) {
         if (data[i].subscriptions) {
           return data[i].subscriptions.map((val: SubscriptionGroupDetails) => val.topic);
         } else if (data[i].groups) {
           return this.getAllTopics(data[i].groups);
         }
       }
     }
     if (data && data.groups) {
      return this.getAllTopics(data.groups);
     }
     return data.subscriptions.map((val: SubscriptionGroupDetails) => val.topic);
}

@ScottSauyet Maybe not, but there's no recursion (at least obvious) in the provided example, maybe the answers in the linked post give some ideas. — Teemu
– Teemu, Commented Feb 14, 2020 at 15:53

Nina Scholz · Accepted Answer · 2020-02-14 16:36:40Z

You could take a recursive approach and check

if the handed over data is not an object for checking, then return with empty array,
if the object has the wanted property, then return an array with the value of topic,
or get the values and make a recursive call with the function and return an array with the result of it.

function getTopics(object) {
    if (!object || typeof object !== 'object') return [];
    if ('topic' in object) return [object.topic];
    return Object.values(object).reduce((r, v) => [...r, ...getTopics(v)], []);
}

var data = { groups: [{ name: "Event", groups: [{ name: "Service", subscriptions: [{ topic: "SERVICE_STATUS_PRESETS" }, { topic: "AIRCRAFT_ACTIVATION" }, { topic: "OUT_OF_SERVICE" }] }] }, { name: "Enquiries", groups: [{ name: "Service-related", subscriptions: [{ topic: "PROMO_CODES_REQUESTS" }] }] }], subscriptions: [{ topic: "BANNERS" }, { topic: "DOCUMENTS" }, { topic: "USER" }] },
    result = getTopics(data);

console.log(result);

vincent · Accepted Answer · 2021-01-07 01:01:16Z

Here is a solution using object-scan

// const objectScan = require('object-scan');

const data = {"groups":[{"name":"Event","groups":[{"name":"Service","subscriptions":[{"topic":"SERVICE_STATUS_PRESETS"},{"topic":"AIRCRAFT_ACTIVATION"},{"topic":"OUT_OF_SERVICE"}]}]},{"name":"Enquiries","groups":[{"name":"Service-related","subscriptions":[{"topic":"PROMO_CODES_REQUESTS"}]}]}],"subscriptions":[{"topic":"BANNERS"},{"topic":"DOCUMENTS"},{"topic":"USER"}]};

const searchTopics = (obj) => objectScan(['**.topic'], { rtn: 'value' })(obj);

console.log(searchTopics(data));
/* => [
  'USER',
  'DOCUMENTS',
  'BANNERS',
  'PROMO_CODES_REQUESTS',
  'OUT_OF_SERVICE',
  'AIRCRAFT_ACTIVATION',
  'SERVICE_STATUS_PRESETS'
] */

.as-console-wrapper {max-height: 100% !important; top: 0}

<script src="https://bundle.run/[email protected]"></script>

Disclaimer: I'm the author of object-scan

Yosef Tukachinsky · Accepted Answer · 2020-02-14 16:20:07Z

use this:

function getTopics(obj){
   if(typeof obj !== 'object') return [];
   if(obj.topic) return [obj.topic];
   var res = [];
   for(var i in obj){
     res.push(...getTopics(obj[i]));
   }
   return res;
}

Working example:

const topics = {
"groups": [
    {
        "name": "Event",
        "groups": [
            {
                "name": "Service",
                "subscriptions": [
                    {
                        "topic": "SERVICE_STATUS_PRESETS"
                    },
                    {
                        "topic": "AIRCRAFT_ACTIVATION",

                    },
                    {
                        "topic": "OUT_OF_SERVICE",

                    }
                ]
            }
        ]
    },
    {
        "name": "Enquiries",
        "groups": [
            {
                "name": "Service-related",
                "subscriptions": [
                    {

                        "topic": "PROMO_CODES_REQUESTS",

                    }
                ]
            }
        ]
    }
],
"subscriptions": [
    {
        "topic": "BANNERS",
    },
    {
        "topic": "DOCUMENTS",
    },
    {
        "topic": "USER",
    }
]
}

function getTopics(obj){
  if(typeof obj !== 'object') return [];
  if(obj.topic) return [obj.topic];
  var res = [];
  for(var i in obj){
    res.push(...getTopics(obj[i]));
  }
  return res;
}


console.log(getTopics(topics));

Brandon · Accepted Answer · 2020-02-14 16:55:39Z

1

This version that takes a functional approach if you are interested. There are others above but this is just another way to look at it.

const recursion = object => Object.entries(object).map(([a, b]) => {
  if (a === 'topic') return b;
  if (Array.isArray(b)) return b.map(recursion);
  return [];
}).flat(Infinity);

recursion(obj);

answered Feb 14, 2020 at 16:55

Brandon

1,6173 gold badges25 silver badges46 bronze badges

1 Comment

BigBlueHat Over a year ago

Trade out map() for flatMap() (and remove .flat(Infinity) in this function for a slight performance boost: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

calarin · Accepted Answer · 2020-02-14 15:58:10Z

0

EDIT: Added another way of doing it with .reduce()

You can create an empty array of topics and then navigate through your nested structure recursively, adding a topic each time you come across it, using the javascript .forEach() to cycle through any nested groups or subscriptions.

let topics = [];

let findTopics = obj => {
   if (obj.groups) {
      obj.groups.forEach(findTopics);
   }
   if (obj.subscriptions) {
      obj.subscriptions.forEach(findTopics);
   }
   if (obj.topic) {
      topics.push(obj.topic);
   }
}

findTopics(data);

Or a possibly neater way using .reduce():

let findTopicsRecursive = (topics, obj) => {
   if (obj.groups) {
      topics = obj.groups.reduce(findTopicsRecursive, topics);
   }
   if (obj.subscriptions) {
      topics = obj.subscriptions.reduce(findTopicsRecursive, topics);
   }
   if (obj.topic) {
      topics.push(obj.topic);
   }
   return topics;
}

let findTopics = data => findTopicsRecursive([], data);

let topics = findTopics(data);

edited Feb 14, 2020 at 15:58

answered Feb 14, 2020 at 15:40

calarin

2362 silver badges11 bronze badges

4 Comments

calarin Over a year ago

@YosefTukachinsky you mean to say that this code is very dependent on a specific data structure?

Yosef Tukachinsky Over a year ago

Yes this what I mean indeed

Scott Sauyet Over a year ago

@calarin: See some of the other answers for techniques that do this more generically.

calarin Over a year ago

@scottsauyet YosefTukachinsky Yes good point - I see what you mean!

Collectives™ on Stack Overflow

Recursive data in JSON object

5 Answers 5

Comments

Comments

Comments

1 Comment

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

Comments

1 Comment

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related