How to get all keys with values from nested objects

Question

I'm looking for something kind of like Object.keys but that works for potentially nested objects. It also shouldn't include keys that have object/array values (it should only include keys with immediate string/number/boolean values).

Example A

Input

{
   "check_id":12345,
   "check_name":"Name of HTTP check",
   "check_type":"HTTP"
}

Expected output

[
  "check_id",
  "check_name",
  "check_type"
]

Object.keys would work for flat cases like this, but not for nested cases:

Example B

Input

{
   "check_id":12345,
   "check_name":"Name of HTTP check",
   "check_type":"HTTP",
   "tags":[
     "example_tag"
   ],
   "check_params":{
      "basic_auth":false,
      "params":[
        "size"
      ],
      "encryption": {
        "enabled": true,
      }
   }
}

Expected output

[
  "check_id",
  "check_name",
  "check_type",
  "check_params.basic_auth",
  "check_params.encryption.enabled"
]

Note that this does not include tags, check_params, check_params.params, or check_params.encryption since these values are arrays/objects.

The question

Is there a library that does this? How would you implement it so that it can work with any object, large and nested, or small?

*It also shouldn't include keys that have object/array values* - but in your example B, `check_params` gets added to the list, even tho it's value is an object. — tymeJV, Nov 01 '17 at 20:17
@tymeJV The `Expected output` only contains `check_params.basic_auth` and `check_params.encryption.enabled` (the nested keys), not the `check_params` itself that has the object value. — , Nov 01 '17 at 20:21

Olian04 · Accepted Answer · 2020-08-31T12:32:30.777

You could use reduce like this:

const keyify = (obj, prefix = '') => 
  Object.keys(obj).reduce((res, el) => {
    if( Array.isArray(obj[el]) ) {
      return res;
    } else if( typeof obj[el] === 'object' && obj[el] !== null ) {
      return [...res, ...keyify(obj[el], prefix + el + '.')];
    }
    return [...res, prefix + el];
  }, []);

const input = {
   "check_id":12345,
   "check_name":"Name of HTTP check",
   "check_type":"HTTP",
   "tags":[
     "example_tag"
   ],
   "check_params":{
      "basic_auth":false,
      "params":[
        "size"
      ],
      "encryption": {
        "enabled": true,
        "testNull": null,
      }
   }
};

const output = keyify(input);

console.log(output);

Edit1: For the general case where you want to include arrays.

const keyify = (obj, prefix = '') => 
  Object.keys(obj).reduce((res, el) => {
    if( typeof obj[el] === 'object' && obj[el] !== null ) {
      return [...res, ...keyify(obj[el], prefix + el + '.')];
    }
    return [...res, prefix + el];
  }, []);

const input = {
   "check_id":12345,
   "check_name":"Name of HTTP check",
   "check_type":"HTTP",
   "tags":[
     "example_tag"
   ],
   "nested": [
      { "foo": 0 },
      { "bar": 1 }
   ],
   "check_params":{
      "basic_auth":false,
      "params":[
        "size"
      ],
      "encryption": {
        "enabled": true,
        "testNull": null,
      }
   }
};

const output = keyify(input);

console.log(output);

maybe you change the value of `enabled` from `true` to `null`, then it does not work, because you are missing a check. — Nina Scholz, Nov 01 '17 at 21:36
I have a similar question when we want to return all keys, please add this object { a: 1, b: 2, c: ["a", "b", "c"], z: { a: "j", q: "q" } it will return ["a", "b", "z.a", "z.q"], how can i show all keys like c? — Yasin Farmani, Nov 27 '20 at 16:59
@YasinFarmani look at the end of my answer. "Edit1: For the general case where you want to include arrays." — Olian04, Nov 27 '20 at 21:25

Mulan · Answer 2 · 2020-08-31T14:55:13.970

A generator makes quick work of this kind of problem -

function* deepKeys (t, pre = [])
{ if (Array.isArray(t))
    return
  else if (Object(t) === t)
    for (const [k, v] of Object.entries(t))
      yield* deepKeys(v, [...pre, k])
  else
    yield pre.join(".")
}

const input =
  {check_id:12345,check_name:"Name of HTTP check",check_type:"HTTP",tags:["example_tag"],check_params:{basic_auth:false,params:["size"],encryption:{enabled:true,testNull:null,}}}
 
console.log(Array.from(deepKeys(input)))

[ "check_id"
, "check_name"
, "check_type"
, "check_params.basic_auth"
, "check_params.encryption.enabled"
, "check_params.encryption.testNull"
]

Or a pure functional expression which eagerly computes all keys -

const deepKeys = (t, pre = []) =>
  Array.isArray(t)
    ? []
: Object(t) === t
   ? Object
      .entries(t)
      .flatMap(([k, v]) => deepKeys(v, [...pre, k]))
: pre.join(".")

const input =
  {check_id:12345,check_name:"Name of HTTP check",check_type:"HTTP",tags:["example_tag"],check_params:{basic_auth:false,params:["size"],encryption:{enabled:true,testNull:null,}}}
 
console.log(deepKeys(input))

[ "check_id"
, "check_name"
, "check_type"
, "check_params.basic_auth"
, "check_params.encryption.enabled"
, "check_params.encryption.testNull"
]

score 2 · Answer 3 · answered Nov 01 '17 at 20:54

You could check the keys and iterate otherwise push the path to the result set.

function getKeys(object) {
    function iter(o, p) {
        if (Array.isArray(o)) { return; }
        if (o && typeof o === 'object') {
            var keys = Object.keys(o);
            if (keys.length) {
                keys.forEach(function (k) { iter(o[k], p.concat(k)); });
            }
            return;
        }
        result.push(p.join('.'));
    }
    var result = [];
    iter(object, []);
    return result;
}

var object = { check_id: 12345, check_name: "Name of HTTP check", check_type: "HTTP", tags: ["example_tag"], check_params: { basic_auth: false, params: ["size"], encryption: { enabled: true } } };

console.log(getKeys(object));

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

score 1 · Answer 4 · answered Nov 01 '17 at 20:39

You can use for...in and create recursive function.

var obj = {"check_id":12345,"check_name":"Name of HTTP check","check_type":"HTTP","tags":["example_tag"],"check_params":{"basic_auth":false,"params":["size",{"a":"b"}],"encryption":{"enabled":true}}}

var keys = []
function getKeys(data, k = '') {
  for (var i in data) {
    var rest = k.length ? '.' + i : i

    if (typeof data[i] == 'object') {
      if (!Array.isArray(data[i])) {
        getKeys(data[i], k + rest)
      }
    } else keys.push(k + rest)
  }
}

getKeys(obj)
console.log(keys)

Having such blatantly unnecessary side effects as a global `keys` variable might convey the wrong message to new JS programmers. Just a thought though. — Olian04, Nov 01 '17 at 20:43

score 0 · Answer 5 · answered Nov 11 '21 at 14:01

var json = {
    id: '1234',
    test: 'terst',
    user : {
        name: '',
        details: {
            address: {
                    add2: {
                        prim: "",
                        sec: ""
                    },
                    add1: '',
            }
        }
    },
    salary: {
      cur: 1234,
      net: 89797
    },
    age: 12
}

let arr = [];
let initialObj = {};

function getKeys(obj, parentK=''){
  initialObj = arr.length === 0 ? obj: initialObj;
  const entries = Object.entries(obj);
  for(let i=0; i<entries.length; i++) {
    const key = entries[i][0];
    const val = entries[i][1];
    const isRootElement = initialObj.hasOwnProperty(key);
    parentK = isRootElement ? key: parentK+'.'+key;
    arr.push(parentK)
    if(typeof val === 'object' && val!==null && !Array.isArray(val)){
      getKeys(val, parentK);
    }
  }
}

getKeys(json)

console.log('arr final---', arr);

score 0 · Answer 6 · answered Jan 23 '23 at 09:42

Further enhanced above recommendation to return all keys including array.

 const keyify = (obj, prefix = '') => 
  Object.keys(obj).reduce((res, el) => {
    if( Array.isArray(obj[el]) ) {
      return [...res,`${el}: ${obj[el].toString()}`];
    } else if( typeof obj[el] === 'object' && obj[el] !== null ) {
      return [...res,...keyify(obj[el],`${prefix}${el}.`)];
    }
    return [...res,`${prefix}${el}: ${obj[el]}`];
  }, []);
  
const input = {
   "check_id":12345,
   "check_name":"Name of HTTP check",
   "check_type":"HTTP",
   "tags":[
     "example_tag"
   ],
   "check_params":{
      "basic_auth":false,
      "params":[
        "size"
      ],
      "encryption": {
        "enabled": true,
        "testNull": null,
      }
   }
};

const output = keyify(input);
console.log(output);

Expected output:

[
  'check_id: 12345',
  'check_name: Name of HTTP check',
  'check_type: HTTP',
  'tags: example_tag',
  'check_params.basic_auth: false',
  'params: size',
  'check_params.encryption.enabled: true',
  'check_params.encryption.testNull: null'
]

You might want to read _[How do I create a runnable stack snippet?](https://meta.stackoverflow.com/questions/358992)_. — Scott Sauyet, Jan 23 '23 at 14:07
Also, note that this is an odd output format, and an odd way to extend the OP's requirements. Wouldn't this be more appropriate: `{'check_id': 12345, ..., 'check_params.encryption.testNull': null}` ? It wouldn't be much more difficult to generate. — Scott Sauyet, Jan 23 '23 at 14:18

score -1 · Answer 7 · answered Nov 01 '17 at 20:30

Is this what you mean?

http://jsfiddle.net/robbiemilejczak/hfe12brb/1/

I couldn't do it with vanilla JS, and this is a pretty hacky solution that relies on lodash. Basically leverages lodashs _.forIn and _.isArray functions to iterate over an object. Also this will only go 1 layer deep, so objects inside of nested objects will be ignored. It does produce your expected output though, so I'd say it's a decent starting point.

How to get all keys with values from nested objects

Example A

Input

Expected output

Example B

Input

Expected output

The question

7 Answers7

Linked

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