Find all values by specific key in a deep nested object

Question

How would I find all values by specific key in a deep nested object?

For example, if I have an object like this:

const myObj = {
  id: 1,
  children: [
    {
      id: 2,
      children: [
        {
          id: 3
        }
      ]
    },
    {
      id: 4,
      children: [
        {
          id: 5,
          children: [
            {
              id: 6,
              children: [
                {
                  id: 7,
                }
              ]
            }
          ]
        }
      ]
    },
  ]
}

How would I get an array of all values throughout all nests of this obj by the key of id.

Note: children is a consistent name, and id's won't exist outside of a children object.

So from the obj, I would like to produce an array like this:

const idArray = [1, 2, 3, 4, 5, 6, 7]

score 29 · Answer 1 · answered Aug 27 '19 at 23:29

29

This is a bit late but for anyone else finding this, here is a clean, generic recursive function:

function findAllByKey(obj, keyToFind) {
  return Object.entries(obj)
    .reduce((acc, [key, value]) => (key === keyToFind)
      ? acc.concat(value)
      : (typeof value === 'object')
      ? acc.concat(findAllByKey(value, keyToFind))
      : acc
    , [])
}

// USAGE
findAllByKey(myObj, 'id')

answered Aug 27 '19 at 23:29

Steve Holgado

11,508
3
24
32

3

super clean, works well, easy cut & paste. Best answer. – nwales Sep 16 '19 at 01:37
This saved me a bit of time and is fun to consider to boot. Thank you! – Brandon Minton May 13 '21 at 05:37
1

Changed line 5 to `: (typeof value === 'object' && value)` because for some reason, `typeof null === "object"`. – luek baja May 25 '21 at 13:30
Best solution so far, thanks a ton Steve – Balram Singh Jun 14 '22 at 05:52
What would the type-safe version of this function look like? – yumba May 27 '23 at 00:01

score 12 · Accepted Answer · answered Feb 24 '19 at 22:42

You could make a recursive function like this:

idArray = []

function func(obj) {
  idArray.push(obj.id)
  if (!obj.children) {
    return
  }

  obj.children.forEach(child => func(child))
}

Snippet for your sample:

const myObj = {
  id: 1,
  children: [{
      id: 2,
      children: [{
        id: 3
      }]
    },
    {
      id: 4,
      children: [{
        id: 5,
        children: [{
          id: 6,
          children: [{
            id: 7,
          }]
        }]
      }]
    },
  ]
}

idArray = []

function func(obj) {
  idArray.push(obj.id)
  if (!obj.children) {
    return
  }

  obj.children.forEach(child => func(child))
}

func(myObj)
console.log(idArray)

RaaaCode · Answer 3 · 2020-05-06T11:18:42.527

I found steve's answer to be most suited for my needs in extrapolating this out and creating a general recursive function. That said, I encountered issues when dealing with nulls and undefined values, so I extended the condition to accommodate for this. This approach uses:

Array.reduce() - It uses an accumulator function which appends the value's onto the result array. It also splits each object into it's key:value pair which allows you to take the following steps:

Have you've found the key? If so, add it to the array;
If not, have I found an object with values? If so, the key is possibly within there. Keep digging by calling the function on this object and append the result onto the result array; and
Finally, if this is not an object, return the result array unchanged.

Hope it helps!

const myObj = {
  id: 1,
  children: [{
      id: 2,
      children: [{
        id: 3
      }]
    },
    {
      id: 4,
      children: [{
        id: 5,
        children: [{
          id: 6,
          children: [{
            id: 7,
          }]
        }]
      }]
    },
  ]
}

function findAllByKey(obj, keyToFind) {
  return Object.entries(obj)
    .reduce((acc, [key, value]) => (key === keyToFind)
      ? acc.concat(value)
      : (typeof value === 'object' && value)
      ? acc.concat(findAllByKey(value, keyToFind))
      : acc
    , []) || [];
}

const ids = findAllByKey(myObj, 'id');

console.log(ids)

InternalError: too much recursion – Aadam Jun 15 '20 at 21:30 — Aadam, Jun 15 '20 at 21:30
Have you got an example object? – RaaaCode Jun 15 '20 at 21:34 — RaaaCode, Jun 15 '20 at 21:34
Awesome. Exactly what i needed! Works great. – rttmax Apr 23 '21 at 09:23 — rttmax, Apr 23 '21 at 09:23

jo_va · Answer 4 · 2019-02-24T23:03:43.080

You can make a generic recursive function that works with any property and any object.

This uses Object.entries(), Object.keys(), Array.reduce(), Array.isArray(), Array.map() and Array.flat().

The stopping condition is when the object passed in is empty:

const myObj = {
  id: 1,
  anyProp: [{
    id: 2,
    thing: { a: 1, id: 10 },
    children: [{ id: 3 }]
  }, {
    id: 4,
    children: [{
      id: 5,
      children: [{
        id: 6,
        children: [{ id: 7 }]
      }]
    }]
  }]
};

const getValues = prop => obj => {
  if (!Object.keys(obj).length) { return []; }

  return Object.entries(obj).reduce((acc, [key, val]) => {
    if (key === prop) {
      acc.push(val);
    } else {
      acc.push(Array.isArray(val) ? val.map(getIds).flat() : getIds(val));
    }
    return acc.flat();
  }, []);
}

const getIds = getValues('id');

console.log(getIds(myObj));

guest271314 · Answer 5 · 2019-02-25T04:04:03.450

Note: children is a consistent name, and id's wont exist outside of a children object.

So from the obj, I would like to produce an array like this:
const idArray = [1, 2, 3, 4, 5, 6, 7]

Given that the question does not contain any restrictions on how the output is derived from the input and that the input is consistent, where the value of property "id" is a digit and id property is defined only within "children" property, save for case of the first "id" in the object, the input JavaScript plain object can be converted to a JSON string using JSON.stringify(), RegExp /"id":\d+/g matches the "id" property and one or more digit characters following the property name, which is then mapped to .match() the digit portion of the previous match using Regexp \d+ and convert the array value to a JavaScript number using addition operator +

const myObject = {"id":1,"children":[{"id":2,"children":[{"id":3}]},{"id":4,"children":[{"id":5,"children":[{"id":6,"children":[{"id":7}]}]}]}]};

let res = JSON.stringify(myObject).match(/"id":\d+/g).map(m => +m.match(/\d+/));

console.log(res);

JSON.stringify() replacer function can alternatively be used to .push() the value of every "id" property name within the object to an array

const myObject = {"id":1,"children":[{"id":2,"children":[{"id":3}]},{"id":4,"children":[{"id":5,"children":[{"id":6,"children":[{"id":7}]}]}]}]};

const getPropValues = (o, prop) => 
  (res => (JSON.stringify(o, (key, value) => 
    (key === prop && res.push(value), value)), res))([]);

let res = getPropValues(myObject, "id");

console.log(res);

Since the property values of the input to be matched are digits, all the JavaScript object can be converted to a string and RegExp \D can be used to replace all characters that are not digits, spread resulting string to array, and .map() digits to JavaScript numbers

let res = [...JSON.stringify(myObj).replace(/\D/g,"")].map(Number)

Ele · Answer 6 · 2019-02-24T23:03:41.200

Using recursion.

const myObj = {  id: 1,  children: [    {      id: 2,      children: [        {          id: 3        }      ]    },    {      id: 4,      children: [        {          id: 5,          children: [            {              id: 6,              children: [                {                  id: 7,                }              ]            }          ]        }      ]    },  ]},
    loop = (array, key, obj) => {
      if (!obj.children) return;
      obj.children.forEach(c => {
        if (c[key]) array.push(c[key]); // is not present, skip!
        loop(array, key, c);
      });
    },
    arr = myObj["id"] ? [myObj["id"]] : [];
    
loop(arr, "id", myObj);
console.log(arr);

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

Jack Bashford · Answer 7 · 2019-02-25T00:31:16.757

You can make a recursive function with Object.entries like so:

const myObj = {
  id: 1,
  children: [{
      id: 2,
      children: [{
        id: 3
      }]
    },
    {
      id: 4,
      children: [{
        id: 5,
        children: [{
          id: 6,
          children: [{
            id: 7,
          }]
        }]
      }]
    },
  ]
};

function findIds(obj) {
  const entries = Object.entries(obj);
  let result = entries.map(e => {
    if (e[0] == "children") {
      return e[1].map(child => findIds(child));
    } else {
      return e[1];
    }
  });
  function flatten(arr, flat = []) {
    for (let i = 0, length = arr.length; i < length; i++) {
      const value = arr[i];
      if (Array.isArray(value)) {
        flatten(value, flat);
      } else {
        flat.push(value);
      }
    }
    return flat;
  }
  return flatten(result);
}

var ids = findIds(myObj);
console.log(ids);

Flattening function from this answer

ES5 syntax:

var myObj = {
  id: 1,
  children: [{
      id: 2,
      children: [{
        id: 3
      }]
    },
    {
      id: 4,
      children: [{
        id: 5,
        children: [{
          id: 6,
          children: [{
            id: 7,
          }]
        }]
      }]
    },
  ]
};

function findIds(obj) {
  const entries = Object.entries(obj);
  let result = entries.map(function(e) {
    if (e[0] == "children") {
      return e[1].map(function(child) {
        return findIds(child)
      });
    } else {
      return e[1];
    }
  });
  function flatten(arr, flat = []) {
    for (let i = 0, length = arr.length; i < length; i++) {
      const value = arr[i];
      if (Array.isArray(value)) {
        flatten(value, flat);
      } else {
        flat.push(value);
      }
    }
    return flat;
  }
  return flatten(result);
}

var ids = findIds(myObj);
console.log(ids);

No problem @cup_of, I'm glad to help – Jack Bashford Feb 24 '19 at 23:51 — Jack Bashford, Feb 24 '19 at 23:51

score 1 · Answer 8 · answered Sep 23 '21 at 15:18

1

let str = JSON.stringify(myObj);
let array = str.match(/\d+/g).map(v => v * 1);
console.log(array); // [1, 2, 3, 4, 5, 6, 7]

answered Sep 23 '21 at 15:18

SUDHIR KUMAR

381
4
10

vincent · Answer 9 · 2021-01-10T02:19:16.123

We use object-scan for a lot of our data processing needs now. It makes the code much more maintainable, but does take a moment to wrap your head around. Here is how you could use it to answer your question

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

const find = (data, needle) => objectScan([needle], { rtn: 'value' })(data);

const myObj = { id: 1, children: [{ id: 2, children: [ { id: 3 } ] }, { id: 4, children: [ { id: 5, children: [ { id: 6, children: [ { id: 7 } ] } ] } ] }] };

console.log(find(myObj, '**.id'));
// => [ 7, 6, 5, 4, 3, 2, 1 ]

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

<script src="https://bundle.run/object-scan@13.7.1"></script>

Disclaimer: I'm the author of object-scan

score 0 · Answer 10 · answered May 19 '21 at 13:07

0

import {flattenDeep} from 'lodash';

/**
 * Extracts all values from an object (also nested objects)
 * into a single array
 *
 * @param obj
 * @returns
 *
 * @example
 * const test = {
 *  alpha: 'foo',
 *  beta: {
 *    gamma: 'bar',
 *    lambda: 'baz'
 *  }
 * }
 *
 * objectFlatten(test) // ['foo', 'bar', 'baz']
 */
export function objectFlatten(obj: {}) {
  const result = [];
  for (const prop in obj) {
    const value = obj[prop];
    if (typeof value === 'object') {
      result.push(objectFlatten(value));
    } else {
      result.push(value);
    }
  }
  return flattenDeep(result);
}

answered May 19 '21 at 13:07

nanacnote

11
1
4

It would be helpful if you write an explanation on what you example code does. – chrwahl May 19 '21 at 14:48
@chrwahl please see the jsdocs comment above code it even comes with examples. – nanacnote May 19 '21 at 15:38

score 0 · Answer 11 · answered Dec 03 '21 at 15:31

Below solution is generic which will return all values by matching nested keys as well e.g for below json object

{
   "a":1,
   "b":{
      "a":{
         "a":"red"
      }
   },
   "c":{
      "d":2
   }
}

to find all values matching key "a" output should be return

[1,{a:"red"},"red"]

const findkey = (obj, key) => {
  let arr = [];
  if (isPrimitive(obj)) return obj;

  for (let [k, val] of Object.entries(obj)) {
    if (k === key) arr.push(val);
    if (!isPrimitive(val)) arr = [...arr, ...findkey(val, key)];
  }
  return arr;
};

const isPrimitive = (val) => {
  return val !== Object(val);
};

Find all values by specific key in a deep nested object

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