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How to Differentiate Objects that Have Multiple Key/Value Pairs From Objects with String Values in JavaScript [duplicate]

I need to flatten a nested object. Need a one liner. Not sure what the correct term for this process is.
I can use pure Javascript or libraries, I particularly like underscore.
I've got ...
{
a:2,
b: {
c:3
}
}
And I want ...
{
a:2,
c:3
}
I've tried ...
var obj = {"fred":2,"jill":4,"obby":{"john":5}};
var resultObj = _.pick(obj, "fred")
alert(JSON.stringify(resultObj));
Which works but I also need this to work ...
var obj = {"fred":2,"jill":4,"obby":{"john":5}};
var resultObj = _.pick(obj, "john")
alert(JSON.stringify(resultObj));

Here you go:
Object.assign({}, ...function _flatten(o) { return [].concat(...Object.keys(o).map(k => typeof o[k] === 'object' ? _flatten(o[k]) : ({[k]: o[k]})))}(yourObject))
Summary: recursively create an array of one-property objects, then combine them all with Object.assign.
This uses ES6 features including Object.assign or the spread operator, but it should be easy enough to rewrite not to require them.
For those who don't care about the one-line craziness and would prefer to be able to actually read it (depending on your definition of readability):
Object.assign(
{},
...function _flatten(o) {
return [].concat(...Object.keys(o)
.map(k =>
typeof o[k] === 'object' ?
_flatten(o[k]) :
({[k]: o[k]})
)
);
}(yourObject)
)

Simplified readable example, no dependencies
/**
* Flatten a multidimensional object
*
* For example:
* flattenObject{ a: 1, b: { c: 2 } }
* Returns:
* { a: 1, c: 2}
*/
export const flattenObject = (obj) => {
const flattened = {}
Object.keys(obj).forEach((key) => {
const value = obj[key]
if (typeof value === 'object' && value !== null && !Array.isArray(value)) {
Object.assign(flattened, flattenObject(value))
} else {
flattened[key] = value
}
})
return flattened
}
Features
No dependencies
Works with null values
Works with arrays
Working example https://jsfiddle.net/webbertakken/jn613d8p/26/

Here is a true, crazy one-liner that flats the nested object recursively:
const flatten = (obj, roots=[], sep='.') => Object.keys(obj).reduce((memo, prop) => Object.assign({}, memo, Object.prototype.toString.call(obj[prop]) === '[object Object]' ? flatten(obj[prop], roots.concat([prop]), sep) : {[roots.concat([prop]).join(sep)]: obj[prop]}), {})
Multiline version, explained:
// $roots keeps previous parent properties as they will be added as a prefix for each prop.
// $sep is just a preference if you want to seperate nested paths other than dot.
const flatten = (obj, roots = [], sep = '.') => Object
// find props of given object
.keys(obj)
// return an object by iterating props
.reduce((memo, prop) => Object.assign(
// create a new object
{},
// include previously returned object
memo,
Object.prototype.toString.call(obj[prop]) === '[object Object]'
// keep working if value is an object
? flatten(obj[prop], roots.concat([prop]), sep)
// include current prop and value and prefix prop with the roots
: {[roots.concat([prop]).join(sep)]: obj[prop]}
), {})
An example:
const obj = {a: 1, b: 'b', d: {dd: 'Y'}, e: {f: {g: 'g'}}}
const flat = flatten(obj)
{
'a': 1,
'b': 'b',
'd.dd': 'Y',
'e.f.g': 'g'
}
Happy one-liner day!

ES6 Native, Recursive:
One-liner
const crushObj = (obj) => Object.keys(obj).reduce((acc, cur) => typeof obj[cur] === 'object' ? { ...acc, ...crushObj(obj[cur]) } : { ...acc, [cur]: obj[cur] } , {})
Expanded
const crushObj = (obj = {}) => Object.keys(obj || {}).reduce((acc, cur) => {
if (typeof obj[cur] === 'object') {
acc = { ...acc, ...crushObj(obj[cur])}
} else { acc[cur] = obj[cur] }
return acc
}, {})
Usage
const obj = {
a:2,
b: {
c:3
}
}
const crushed = crushObj(obj)
console.log(crushed)
// { a: 2, c: 3 }

My ES6 version:
const flatten = (obj) => {
let res = {};
for (const [key, value] of Object.entries(obj)) {
if (typeof value === 'object') {
res = { ...res, ...flatten(value) };
} else {
res[key] = value;
}
}
return res;
}

It's not quite a one liner, but here's a solution that doesn't require anything from ES6. It uses underscore's extend method, which could be swapped out for jQuery's.
function flatten(obj) {
var flattenedObj = {};
Object.keys(obj).forEach(function(key){
if (typeof obj[key] === 'object') {
$.extend(flattenedObj, flatten(obj[key]));
} else {
flattenedObj[key] = obj[key];
}
});
return flattenedObj;
}

I like this code because it's a bit easier to understand.
Edit: I added some functionality I needed, so now it's a bit harder to understand.
const data = {
a: "a",
b: {
c: "c",
d: {
e: "e",
f: [
"g",
{
i: "i",
j: {},
k: []
}
]
}
}
};
function flatten(data, response = {}, flatKey = "", onlyLastKey = false) {
for (const [key, value] of Object.entries(data)) {
let newFlatKey;
if (!isNaN(parseInt(key)) && flatKey.includes("[]")) {
newFlatKey = (flatKey.charAt(flatKey.length - 1) == "." ? flatKey.slice(0, -1) : flatKey) + `[${key}]`;
} else if (!flatKey.includes(".") && flatKey.length > 0) {
newFlatKey = `${flatKey}.${key}`;
} else {
newFlatKey = `${flatKey}${key}`;
}
if (typeof value === "object" && value !== null && Object.keys(value).length > 0) {
flatten(value, response, `${newFlatKey}.`, onlyLastKey);
} else {
if(onlyLastKey){
newFlatKey = newFlatKey.split(".").pop();
}
if (Array.isArray(response)) {
response.push({
[newFlatKey.replace("[]", "")]: value
});
} else {
response[newFlatKey.replace("[]", "")] = value;
}
}
}
return response;
}
console.log(flatten(data));
console.log(flatten(data, {}, "data"));
console.log(flatten(data, {}, "data[]"));
console.log(flatten(data, {}, "data", true));
console.log(flatten(data, {}, "data[]", true));
console.log(flatten(data, []));
console.log(flatten(data, [], "data"));
console.log(flatten(data, [], "data[]"));
console.log(flatten(data, [], "data", true));
console.log(flatten(data, [], "data[]", true));
Demo https://stackblitz.com/edit/typescript-flatter
For insinde a typescript class use:
function flatten(data: any, response = {}, flatKey = "", onlyLastKey = false) {
for (const [key, value] of Object.entries(data)) {
let newFlatKey: string;
if (!isNaN(parseInt(key)) && flatKey.includes("[]")) {
newFlatKey = (flatKey.charAt(flatKey.length - 1) == "." ? flatKey.slice(0, -1) : flatKey) + `[${key}]`;
} else if (!flatKey.includes(".") && flatKey.length > 0) {
newFlatKey = `${flatKey}.${key}`;
} else {
newFlatKey = `${flatKey}${key}`;
}
if (typeof value === "object" && value !== null && Object.keys(value).length > 0) {
flatten(value, response, `${newFlatKey}.`, onlyLastKey);
} else {
if(onlyLastKey){
newFlatKey = newFlatKey.split(".").pop();
}
if (Array.isArray(response)) {
response.push({
[newFlatKey.replace("[]", "")]: value
});
} else {
response[newFlatKey.replace("[]", "")] = value;
}
}
}
return response;
}

This is a function I've got in my common libraries for exactly this purpose.
I believe I got this from a similar stackoverflow question, but cannot remember which (edit: Fastest way to flatten / un-flatten nested JSON objects - Thanks Yoshi!)
function flatten(data) {
var result = {};
function recurse (cur, prop) {
if (Object(cur) !== cur) {
result[prop] = cur;
} else if (Array.isArray(cur)) {
for(var i=0, l=cur.length; i<l; i++)
recurse(cur[i], prop + "[" + i + "]");
if (l == 0)
result[prop] = [];
} else {
var isEmpty = true;
for (var p in cur) {
isEmpty = false;
recurse(cur[p], prop ? prop+"."+p : p);
}
if (isEmpty && prop)
result[prop] = {};
}
}
recurse(data, "");
return result;
}
This can then be called as follows:
var myJSON = '{a:2, b:{c:3}}';
var myFlattenedJSON = flatten(myJSON);
You can also append this function to the standard Javascript string class as follows:
String.prototype.flattenJSON = function() {
var data = this;
var result = {};
function recurse (cur, prop) {
if (Object(cur) !== cur) {
result[prop] = cur;
} else if (Array.isArray(cur)) {
for(var i=0, l=cur.length; i<l; i++)
recurse(cur[i], prop + "[" + i + "]");
if (l == 0)
result[prop] = [];
} else {
var isEmpty = true;
for (var p in cur) {
isEmpty = false;
recurse(cur[p], prop ? prop+"."+p : p);
}
if (isEmpty && prop)
result[prop] = {};
}
}
recurse(data, "");
return result;
}
With which, you can do the following:
var flattenedJSON = '{a:2, b:{c:3}}'.flattenJSON();

Here are vanilla solutions that work for arrays, primitives, regular expressions, functions, any number of nested object levels, and just about everything else I could throw at them. The first overwrites property values in the manner that you would expect from Object.assign.
((o) => {
return o !== Object(o) || Array.isArray(o) ? {}
: Object.assign({}, ...function leaves(o) {
return [].concat.apply([], Object.entries(o)
.map(([k, v]) => {
return (( !v || typeof v !== 'object'
|| !Object.keys(v).some(key => v.hasOwnProperty(key))
|| Array.isArray(v))
? {[k]: v}
: leaves(v)
);
})
);
}(o))
})(o)
The second accumulates values into an array.
((o) => {
return o !== Object(o) || Array.isArray(o) ? {}
: (function () {
return Object.values((function leaves(o) {
return [].concat.apply([], !o ? [] : Object.entries(o)
.map(([k, v]) => {
return (( !v || typeof v !== 'object'
|| !Object.keys(v).some(k => v.hasOwnProperty(k))
|| (Array.isArray(v) && !v.some(el => typeof el === 'object')))
? {[k]: v}
: leaves(v)
);
})
);
}(o))).reduce((acc, cur) => {
return ((key) => {
acc[key] = !acc[key] ? [cur[key]]
: new Array(...new Set(acc[key].concat([cur[key]])))
})(Object.keys(cur)[0]) ? acc : acc
}, {})
})(o);
})(o)
Also please do not include code like this in production as it is terribly difficult to debug.
function leaves1(o) {
return ((o) => {
return o !== Object(o) || Array.isArray(o) ? {}
: Object.assign({}, ...function leaves(o) {
return [].concat.apply([], Object.entries(o)
.map(([k, v]) => {
return (( !v || typeof v !== 'object'
|| !Object.keys(v).some(key => v.hasOwnProperty(key))
|| Array.isArray(v))
? {[k]: v}
: leaves(v)
);
})
);
}(o))
})(o);
}
function leaves2(o) {
return ((o) => {
return o !== Object(o) || Array.isArray(o) ? {}
: (function () {
return Object.values((function leaves(o) {
return [].concat.apply([], !o ? [] : Object.entries(o)
.map(([k, v]) => {
return (( !v || typeof v !== 'object'
|| !Object.keys(v).some(k => v.hasOwnProperty(k))
|| (Array.isArray(v) && !v.some(el => typeof el === 'object')))
? {[k]: v}
: leaves(v)
);
})
);
}(o))).reduce((acc, cur) => {
return ((key) => {
acc[key] = !acc[key] ? [cur[key]]
: new Array(...new Set(acc[key].concat([cur[key]])))
})(Object.keys(cur)[0]) ? acc : acc
}, {})
})(o);
})(o);
}
const obj = {
l1k0: 'foo',
l1k1: {
l2k0: 'bar',
l2k1: {
l3k0: {},
l3k1: null
},
l2k2: undefined
},
l1k2: 0,
l2k3: {
l3k2: true,
l3k3: {
l4k0: [1,2,3],
l4k1: [4,5,'six', {7: 'eight'}],
l4k2: {
null: 'test',
[{}]: 'obj',
[Array.prototype.map]: Array.prototype.map,
l5k3: ((o) => (typeof o === 'object'))(this.obj),
}
}
},
l1k4: '',
l1k5: new RegExp(/[\s\t]+/g),
l1k6: function(o) { return o.reduce((a,b) => a+b)},
false: [],
}
const objs = [null, undefined, {}, [], ['non', 'empty'], 42, /[\s\t]+/g, obj];
objs.forEach(o => {
console.log(leaves1(o));
});
objs.forEach(o => {
console.log(leaves2(o));
});

Here's an ES6 version in TypeScript. It takes the best of answers given here and elsewhere. Some features:
Supports Date objects and converts them into ISO strings
Puts an underscore between the parent's and child's key (e.g. {a: {b: 'test'}} becomes {a_b: 'test'}
const flatten = (obj: Record<string, unknown>, parent?: string): Record<string, unknown> => {
let res: Record<string, unknown> = {}
for (const [key, value] of Object.entries(obj)) {
const propName = parent ? parent + '_' + key : key
const flattened: Record<string, unknown> = {}
if (value instanceof Date) {
flattened[key] = value.toISOString()
} else if(typeof value === 'object' && value !== null){
res = {...res, ...flatten(value as Record<string, unknown>, propName)}
} else {
res[propName] = value
}
}
return res
}
An example:
const example = {
person: {
firstName: 'Demo',
lastName: 'Person'
},
date: new Date(),
hello: 'world'
}
// becomes
const flattenedExample = {
person_firstName: 'Demo',
person_lastName: 'Person',
date: '2021-10-18T10:41:14.278Z',
hello: 'world'
}

Here is an actual oneliner of just 91 characters, using Underscore. (Of course. What else?)
var { reduce, isObject } = _;
var data = {
a: 1,
b: 2,
c: {
d: 3,
e: 4,
f: {
g: 5
},
h: 6
}
};
var tip = (v, m={}) => reduce(v, (m, v, k) => isObject(v) ? tip(v, m) : {...m, [k]: v}, m);
console.log(tip(data));
<script src="https://underscorejs.org/underscore-umd-min.js"></script>
Readable version:
var { reduce, isObject, extend } = _;
var data = {
a: 1,
b: 2,
c: {
d: 3,
e: 4,
f: {
g: 5
},
h: 6
}
};
// This function is passed to _.reduce below.
// We visit a single key of the input object. If the value
// itself is an object, we recursively copy its keys into
// the output object (memo) by calling tip. Otherwise we
// add the key-value pair to the output object directly.
function tipIteratee(memo, value, key) {
if (isObject(value)) return tip(value, memo);
return extend(memo, {[key]: value});
}
// The entry point of the algorithm. Walks over the keys of
// an object using _.reduce, collecting all tip keys in memo.
function tip(value, memo = {}) {
return _.reduce(value, tipIteratee, memo);
}
console.log(tip(data));
<script src="https://underscorejs.org/underscore-umd-min.js"></script>
Also works with Lodash.

To flatten only the first level of the object and merge duplicate object keys into an array:
var myObj = {
id: '123',
props: {
Name: 'Apple',
Type: 'Fruit',
Link: 'apple.com',
id: '345'
},
moreprops: {
id: "466"
}
};
const flattenObject = (obj) => {
let flat = {};
for (const [key, value] of Object.entries(obj)) {
if (typeof value === 'object' && value !== null) {
for (const [subkey, subvalue] of Object.entries(value)) {
// avoid overwriting duplicate keys: merge instead into array
typeof flat[subkey] === 'undefined' ?
flat[subkey] = subvalue :
Array.isArray(flat[subkey]) ?
flat[subkey].push(subvalue) :
flat[subkey] = [flat[subkey], subvalue]
}
} else {
flat = {...flat, ...{[key]: value}};
}
}
return flat;
}
console.log(flattenObject(myObj))

Object.assign requires a polyfill. This version is similar to previous ones, but it is not using Object.assign and it is still keep tracking of parent's name
const flatten = (obj, parent = null) => Object.keys(obj).reduce((acc, cur) =>
typeof obj[cur] === 'object' ? { ...acc, ...flatten(obj[cur], cur) } :
{ ...acc, [((parent) ? parent + '.' : "") + cur]: obj[cur] } , {})
const obj = {
a:2,
b: {
c:3
}
}
const flattened = flatten(obj)
console.log(flattened)

Here is a flatten function that correctly outputs array indexes.
function flatten(obj) {
const result = {};
for (const key of Object.keys(obj)) {
if (typeof obj[key] === 'object') {
const nested = flatten(obj[key]);
for (const nestedKey of Object.keys(nested)) {
result[`${key}.${nestedKey}`] = nested[nestedKey];
}
} else {
result[key] = obj[key];
}
}
return result;
}
Example Input:
{
"first_name": "validations.required",
"no_middle_name": "validations.required",
"last_name": "validations.required",
"dob": "validations.required",
"citizenship": "validations.required",
"citizenship_identity": {
"name": "validations.required",
"value": "validations.required"
},
"address": [
{
"country_code": "validations.required",
"street": "validations.required",
"city": "validations.required",
"state": "validations.required",
"zipcode": "validations.required",
"start_date": "validations.required",
"end_date": "validations.required"
},
{
"country_code": "validations.required",
"street": "validations.required",
"city": "validations.required",
"state": "validations.required",
"zipcode": "validations.required",
"start_date": "validations.required",
"end_date": "validations.required"
}
]
}
Example Output:
const flattenedOutput = flatten(inputObj);
{
"first_name": "validations.required",
"no_middle_name": "validations.required",
"last_name": "validations.required",
"dob": "validations.required",
"citizenship": "validations.required",
"citizenship_identity.name": "validations.required",
"citizenship_identity.value": "validations.required",
"address.0.country_code": "validations.required",
"address.0.street": "validations.required",
"address.0.city": "validations.required",
"address.0.state": "validations.required",
"address.0.zipcode": "validations.required",
"address.0.start_date": "validations.required",
"address.0.end_date": "validations.required",
"address.1.country_code": "validations.required",
"address.1.street": "validations.required",
"address.1.city": "validations.required",
"address.1.state": "validations.required",
"address.1.zipcode": "validations.required",
"address.1.start_date": "validations.required",
"address.1.end_date": "validations.required"
}

function flatten(obj: any) {
return Object.keys(obj).reduce((acc, current) => {
const key = `${current}`;
const currentValue = obj[current];
if (Array.isArray(currentValue) || Object(currentValue) === currentValue) {
Object.assign(acc, flatten(currentValue));
} else {
acc[key] = currentValue;
}
return acc;
}, {});
};
let obj = {
a:2,
b: {
c:3
}
}
console.log(flatten(obj))
Demo
https://stackblitz.com/edit/typescript-flatten-json

Here goes, not thoroughly tested. Utilizes ES6 syntax too!!
loopValues(val){
let vals = Object.values(val);
let q = [];
vals.forEach(elm => {
if(elm === null || elm === undefined) { return; }
if (typeof elm === 'object') {
q = [...q, ...this.loopValues(elm)];
}
return q.push(elm);
});
return q;
}
let flatValues = this.loopValues(object)
flatValues = flatValues.filter(elm => typeof elm !== 'object');
console.log(flatValues);

I know its been very long, but it may be helpful for some one in the future
I've used recursion
let resObj = {};
function flattenObj(obj) {
for (let key in obj) {
if (!(typeof obj[key] == 'object')) {
// console.log('not an object', key);
resObj[key] = obj[key];
// console.log('res obj is ', resObj);
} else {
flattenObj(obj[key]);
}
}
return resObj;
}

Here's my TypeScript extension from #Webber's answer. Also supports dates:
private flattenObject(obj: any): any {
const flattened = {};
for (const key of Object.keys(obj)) {
if (isNullOrUndefined(obj[key])) {
continue;
}
if (typeof obj[key].getMonth === 'function') {
flattened[key] = (obj[key] as Date).toISOString();
} else if (typeof obj[key] === 'object' && obj[key] !== null) {
Object.assign(flattened, this.flattenObject(obj[key]));
} else {
flattened[key] = obj[key];
}
}
return flattened;
}

const obj = {
a:2,
b: {
c:3
}
}
// recursive function for extracting keys
function extractKeys(obj) {
let flattenedObj = {};
for(let [key, value] of Object.entries(obj)){
if(typeof value === "object") {
flattenedObj = {...flattenedObj, ...extractKeys(value)};
} else {
flattenedObj[key] = value;
}
}
return flattenedObj;
}
// main code
let flattenedObj = extractKeys(obj);
console.log(flattenedObj);

How to remove empty nested objects in an array?

I have an array of objects, that can either have direct or nested values. The goal is to remove all empty fields.
For exemple:
const todos = [ {}, { not: {} } ]
// expected output: []
const todos2 = [ {}, { not: {countries: ["uk", "us"]} } ]
// expected output: [{ not: {countries: ["uk", "us"]} }]
I've tried to filter the array with Object.values.length, it when a nested value is an empty object, it doesn't work anymore. Would someone know how to do it?
EDIT: So I've came up with my own solution which is a bit simpler from what I've read here:
function foo(todos){
todos.map((todo,i)=> {
if(!Object.keys(todo).length){
return todos.splice(i, 1)
}
if(Object.keys(todo).length){
const key = Object.keys(todo) + ""
return !Object.values(todo[key]).length && todos.splice(i, 1)
}
return todo
})
return todos.filter(c=> Object.keys(c).length)
}

Because your structure has a mix of Objects and Arrays, you will want to check for this.
Below is an example.
function trimEmptyObjects(o) {
if (typeof o !== 'object') return o;
if (Array.isArray(o)) {
for (let i = o.length -1; i >= 0; i --) {
o[i] = trimEmptyObjects(o[i]);
if (typeof o[i] === 'object') {
if (!Object.keys(o[i]).length) {
o.splice(i, 1);
}
}
}
return o;
} else {
const e = Object.entries(o);
for (let i = e.length -1; i >= 0; i --) {
e[i][1] = trimEmptyObjects(e[i][1]);
if (typeof e[i][1] === 'object') {
if (!Object.keys(e[i][1]).length) {
e.splice(i, 1);
}
}
}
return Object.fromEntries(e);
}
}
const todos = [ {}, { not: {} } ]
// expected output: []
console.log(trimEmptyObjects(todos));
const todos2 = [ {}, { not: {countries: ["uk", "us"]} } ]
// expected output: [{ not: {countries: ["uk", "us"]} }]
console.log(trimEmptyObjects(todos2));

I think you want like this..
const todos = [ {}, { not: {} } ];
const todos2 = [ {}, { not: {countries: ["uk", "us"]} } ];
function clean(object) {
Object
.entries(object)
.forEach(([k, v]) => {
if (v && typeof v === 'object') {
clean(v);
}
if (v && typeof v === 'object' && !Object.keys(v).length || v === null || v === undefined) {
if (Array.isArray(object)) {
object.splice(k, 1);
} else {
delete object[k];
}
}
});
return object;
}
console.log(clean(todos));
console.log(clean(todos2));

try with filter
const isEmpty = e => Object.entries(e).length
const removeEmptyObject = e => e.not?isEmpty(e.not):isEmpty(e)
const todos = [ {}, { not: {} } ]
console.log(todos.filter(removeEmptyObject))
const todos2 = [ {}, { not: {countries: ["uk", "us"]} } ]
console.log(todos2.filter(removeEmptyObject))

Recursively find keys on an object

I have a javascript object structured like this;
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
Given an array of keys ['brand', 'group', 'newGroup', 'newSubGroup'] I want to split the keys into found and missing keys. So for the structure above I should get back;
present = ['brand', 'group']
missing = ['newGroup', 'newSubGroup']
I'm using ES6 and have lodash available, but struggling to find a clean way to produce this.
This is not to just check existence, it's recursively find the keys and return those present and the remaining ones.

Here's a pretty sketchy way that works.
const find = (keys, obj) => {
const string = JSON.stringify(obj);
return keys.reduce(({ present, missing }, key) => {
const match = string.match(new RegExp(`"${key}":`));
if (match) {
present.push(key);
} else {
missing.push(key);
}
return { present, missing };
}, { present: [], missing: [] });
}

You can use this function made for you ;)
var getAttrs = function(obj) {
return [].concat.apply([], Object.keys(obj).map(function (key) {
var results = [key]
if (typeof obj[key] === 'object') {
Array.prototype.push.apply(results, getAttrs(obj[key]))
}
return results
}))
}
It return the list of properties and children properties.
getAttrs({brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}})
> ["brand", "group", "subGroup", "items", "otherSub", "items"]
And you can use it like so:
var lookingFor = ['brand', 'group', 'newGroup', 'newSubGroup']
var existings = getAttrs(obj)
var missings = []
var presents = []
lookingFor.forEach(attr => {
if (existings.indexOf(attr) === -1) {
missings.push(attr)
} else {
presents.push(attr)
}
})

I wrote a function to recursively get unique keys from a nested object, then filtered the array of all the keys you mentioned checking which were present in the result of my function.
var thisObject = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
};
var arr_full = ['brand', 'group', 'newGroup', 'newSubGroup'] ;
var key_array = [];
function addToKeyArray( key_array, object ){
for( var key in object ){
// only get unique keys
if( key_array.indexOf( key ) === -1 ){
key_array.push( key );
}
// concat the result of calling this function recurrsively on object[key]
key_array.concat( addToKeyArray( key_array, object[key] ) );
}
return key_array;
}
var test = addToKeyArray( [], thisObject );
var missing = arr_full.filter( function( el ) {
return test.indexOf( el ) < 0;
});
console.log( test );
console.log( missing )

You can create recursive function using for...in loop inside another function and return object as result..
var obj = {"brand":{"group":{"subGroup":{"items":[]},"otherSub":{"items":[]}}}}
var keys = ['brand', 'group', 'newGroup', 'newSubGroup'] ;
function findKeys(data, keys) {
keys = keys.slice();
function findPresent(data, keys) {
var result = []
for(var i in data) {
if(typeof data[i] == 'object') result.push(...findPresent(data[i], keys))
var index = keys.indexOf(i);
if(index != -1) result.push(...keys.splice(index, 1))
}
return result
}
return {present: findPresent(data, keys), missing: keys}
}
console.log(findKeys(obj, keys))

To keep things clean and readable you can use "for in", inside a nested function for your recursion.
function recur(obj) {
let preMiss = {
present: [],
missing: []
}
let root = traverse => {
for (let key in traverse) {
if (Array.isArray(traverse[key].items)) {
preMiss.missing.push(key);
}
if (typeof traverse[key] === 'object' && !Array.isArray(traverse[key].items)) {
preMiss.present.push(key);
root(traverse[key])
}
}
}
root(obj);
return preMiss;
}
const object = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
}
console.log(Object.entries(recur(object)));

var toFind = ['brand', 'group', 'newGroup', 'newSubGroup'],
found = [];
var o = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
}
//called with every property and its value
function process(key,value) {
var i = toFind.indexOf(key);
if(i !== -1){
found.push(key);
toFind.splice(i, 1);
}
}
function traverse(o,func) {
if(!toFind.length) return;
for (var i in o) {
func.apply(this,[i,o[i]]);
if (o[i] !== null && typeof(o[i])=="object") {
//going one step down in the object tree!!
traverse(o[i],func);
}
}
}
traverse(o,process);
console.log(found); // present
console.log(toFind); // absent
Traverse method taken from https://stackoverflow.com/a/722732/1335165

Even though this question is a bit older, I want to present a rather short solution to the problem.
const recursivelyGetKeys = obj => Object.keys(obj).map(key => typeof obj[key] === 'object'
? [...recursivelyGetKeys(obj[key]), key] : [key]).reduce((p, c) => [...p, ...c], [])
This function will return all keys in the object, so a call to the array arr with
const arr = {
brand: {
group: {
subGroup: {
items: []
},
otherSub: {
items: []
}
}
}
}
will output:
const keys = recursivelyGetKeys(arr) // = ["items", "subGroup", "items", "otherSub", "group", "brand"]
Now to find the intersection set of this and find = ['brand', 'group', 'newGroup', 'newSubGroup'], do:
const found = keys.filter(key => find.some(val === key))
const missing = keys.filter(key => find.every(val !== key))

Find by key deep in a nested array

Let's say I have an object:
[
{
'title': "some title"
'channel_id':'123we'
'options': [
{
'channel_id':'abc'
'image':'http://asdasd.com/all-inclusive-block-img.jpg'
'title':'All-Inclusive'
'options':[
{
'channel_id':'dsa2'
'title':'Some Recommends'
'options':[
{
'image':'http://www.asdasd.com' 'title':'Sandals'
'id':'1'
'content':{
...
I want to find the one object where the id is 1. Is there a function for something like this? I could use Underscore's _.filter method, but I would have to start at the top and filter down.

Recursion is your friend. I updated the function to account for property arrays:
function getObject(theObject) {
var result = null;
if(theObject instanceof Array) {
for(var i = 0; i < theObject.length; i++) {
result = getObject(theObject[i]);
if (result) {
break;
}
}
}
else
{
for(var prop in theObject) {
console.log(prop + ': ' + theObject[prop]);
if(prop == 'id') {
if(theObject[prop] == 1) {
return theObject;
}
}
if(theObject[prop] instanceof Object || theObject[prop] instanceof Array) {
result = getObject(theObject[prop]);
if (result) {
break;
}
}
}
}
return result;
}
updated jsFiddle: http://jsfiddle.net/FM3qu/7/

Another (somewhat silly) option is to exploit the naturally recursive nature of JSON.stringify, and pass it a replacer function which runs on each nested object during the stringification process:
const input = [{
'title': "some title",
'channel_id': '123we',
'options': [{
'channel_id': 'abc',
'image': 'http://asdasd.com/all-inclusive-block-img.jpg',
'title': 'All-Inclusive',
'options': [{
'channel_id': 'dsa2',
'title': 'Some Recommends',
'options': [{
'image': 'http://www.asdasd.com',
'title': 'Sandals',
'id': '1',
'content': {}
}]
}]
}]
}];
console.log(findNestedObj(input, 'id', '1'));
function findNestedObj(entireObj, keyToFind, valToFind) {
let foundObj;
JSON.stringify(entireObj, (_, nestedValue) => {
if (nestedValue && nestedValue[keyToFind] === valToFind) {
foundObj = nestedValue;
}
return nestedValue;
});
return foundObj;
};

What worked for me was this lazy approach, not algorithmically lazy ;)
if( JSON.stringify(object_name).indexOf("key_name") > -1 ) {
console.log("Key Found");
}
else{
console.log("Key not Found");
}

If you want to get the first element whose id is 1 while object is being searched, you can use this function:
function customFilter(object){
if(object.hasOwnProperty('id') && object["id"] == 1)
return object;
for(var i=0; i<Object.keys(object).length; i++){
if(typeof object[Object.keys(object)[i]] == "object"){
var o = customFilter(object[Object.keys(object)[i]]);
if(o != null)
return o;
}
}
return null;
}
If you want to get all elements whose id is 1, then (all elements whose id is 1 are stored in result as you see):
function customFilter(object, result){
if(object.hasOwnProperty('id') && object.id == 1)
result.push(object);
for(var i=0; i<Object.keys(object).length; i++){
if(typeof object[Object.keys(object)[i]] == "object"){
customFilter(object[Object.keys(object)[i]], result);
}
}
}

Improved #haitaka answer, using the key and predicate
function deepSearch (object, key, predicate) {
if (object.hasOwnProperty(key) && predicate(key, object[key]) === true) return object
for (let i = 0; i < Object.keys(object).length; i++) {
let value = object[Object.keys(object)[i]];
if (typeof value === "object" && value != null) {
let o = deepSearch(object[Object.keys(object)[i]], key, predicate)
if (o != null) return o
}
}
return null
}
So this can be invoked as:
var result = deepSearch(myObject, 'id', (k, v) => v === 1);
or
var result = deepSearch(myObject, 'title', (k, v) => v === 'Some Recommends');
Here is the demo: http://jsfiddle.net/a21dx6c0/
EDITED
In the same way you can find more than one object
function deepSearchItems(object, key, predicate) {
let ret = [];
if (object.hasOwnProperty(key) && predicate(key, object[key]) === true) {
ret = [...ret, object];
}
if (Object.keys(object).length) {
for (let i = 0; i < Object.keys(object).length; i++) {
let value = object[Object.keys(object)[i]];
if (typeof value === "object" && value != null) {
let o = this.deepSearchItems(object[Object.keys(object)[i]], key, predicate);
if (o != null && o instanceof Array) {
ret = [...ret, ...o];
}
}
}
}
return ret;
}

If you're into the whole ES6 thing you can use
const findByKey = (obj, kee) => {
if (kee in obj) return obj[kee];
for(n of Object.values(obj).filter(Boolean).filter(v => typeof v === 'object')) {
let found = findByKey(n, kee)
if (found) return found
}
}
const findByProperty = (obj, predicate) => {
if (predicate(obj)) return obj
for(n of Object.values(obj).filter(Boolean).filter(v => typeof v === 'object')) {
let found = findByProperty(n, predicate)
if (found) return found
}
}
find by value is going to be a little different
let findByValue = (o, val) => {
if (o === val) return o;
if (o === NaN || o === Infinity || !o || typeof o !== 'object') return;
if (Object.values(o).includes(val)) return o;
for (n of Object.values(o)) {
const found = findByValue(n, val)
if (found) return n
}
}
then they can be used like this
const arry = [{ foo: 0 }, null, { bar: [{ baz: { nutherKey: undefined, needle: "gotcha!" } }]}]
const obj = { alice: Infinity, bob: NaN, charlie: "string", david: true, ebert: arry }
findByKey(obj, 'needle')
// 'gotcha!'
findByProperty(obj, val => val.needle === 'gotcha!')
// { nutherKey: undefined, needle: "gotcha!" }
findByValue(obj, 'gotcha!')
// { nutherKey: undefined, needle: "gotcha!" }

I found this page through googling for the similar functionalities. Based on the work provided by Zach and regularmike, I created another version which suits my needs.
BTW, teriffic work Zah and regularmike!
I'll post the code here:
function findObjects(obj, targetProp, targetValue, finalResults) {
function getObject(theObject) {
let result = null;
if (theObject instanceof Array) {
for (let i = 0; i < theObject.length; i++) {
getObject(theObject[i]);
}
}
else {
for (let prop in theObject) {
if(theObject.hasOwnProperty(prop)){
console.log(prop + ': ' + theObject[prop]);
if (prop === targetProp) {
console.log('--found id');
if (theObject[prop] === targetValue) {
console.log('----found porop', prop, ', ', theObject[prop]);
finalResults.push(theObject);
}
}
if (theObject[prop] instanceof Object || theObject[prop] instanceof Array){
getObject(theObject[prop]);
}
}
}
}
}
getObject(obj);
}
What it does is it find any object inside of obj with property name and value matching to targetProp and targetValue and will push it to the finalResults array.
And Here's the jsfiddle to play around:
https://jsfiddle.net/alexQch/5u6q2ybc/

I've created library for this purpose: https://github.com/dominik791/obj-traverse
You can use findFirst() method like this:
var foundObject = findFirst(rootObject, 'options', { 'id': '1' });
And now foundObject variable stores a reference to the object that you're looking for.

Another recursive solution, that works for arrays/lists and objects, or a mixture of both:
function deepSearchByKey(object, originalKey, matches = []) {
if(object != null) {
if(Array.isArray(object)) {
for(let arrayItem of object) {
deepSearchByKey(arrayItem, originalKey, matches);
}
} else if(typeof object == 'object') {
for(let key of Object.keys(object)) {
if(key == originalKey) {
matches.push(object);
} else {
deepSearchByKey(object[key], originalKey, matches);
}
}
}
}
return matches;
}
usage:
let result = deepSearchByKey(arrayOrObject, 'key'); // returns an array with the objects containing the key

You can use javascript some function inside a recursive function. The advantage of some is to stop looping once the child is founded. Do not use map that would be slow in large data.
const findChild = (array, id) => {
let result;
array.some(
(child) =>
(child.id === id && (result = child)) ||
(result = findChild(child.options || [], id))
);
return result;
};
findChild(array, 1)

Just use recursive function.
See example below:
const data = [
{
title: 'some title',
channel_id: '123we',
options: [
{
channel_id: 'abc',
image: 'http://asdasd.com/all-inclusive-block-img.jpg',
title: 'All-Inclusive',
options: [
{
channel_id: 'dsa2',
title: 'Some Recommends',
options: [
{
image: 'http://www.asdasd.com',
title: 'Sandals',
id: '1',
content: {},
}
]
}
]
}
]
}
]
function _find(collection, key, value) {
for (const o of collection) {
for (const [k, v] of Object.entries(o)) {
if (k === key && v === value) {
return o
}
if (Array.isArray(v)) {
const _o = _find(v, key, value)
if (_o) {
return _o
}
}
}
}
}
console.log(_find(data, 'channel_id', 'dsa2'))

We use object-scan for our data processing. It's conceptually very simple, but allows for a lot of cool stuff. Here is how you would solve your specific question
// const objectScan = require('object-scan');
const find = (id, input) => objectScan(['**'], {
abort: true,
rtn: 'value',
filterFn: ({ value }) => value.id === id
})(input);
const data = [{ title: 'some title', channel_id: '123we', options: [{ channel_id: 'abc', image: 'http://asdasd.com/all-inclusive-block-img.jpg', title: 'All-Inclusive', options: [{ channel_id: 'dsa2', title: 'Some Recommends', options: [{ image: 'http://www.asdasd.com', title: 'Sandals', id: '1', content: {} }] }] }] }];
console.log(find('1', data));
// => { image: 'http://www.asdasd.com', title: 'Sandals', id: '1', content: {} }
.as-console-wrapper {max-height: 100% !important; top: 0}
<script src="https://bundle.run/object-scan#13.8.0"></script>
Disclaimer: I'm the author of object-scan

Found the answer I was looking for, especially Ali Alnoaimi's solution. I made some small adjustments to allow for the search of the value as well
function deepSearchByKey(object, originalKey, originalValue, matches = []) {
if (object != null) {
if (Array.isArray(object)) {
for (let arrayItem of object) {
deepSearchByKey(arrayItem, originalKey, originalValue, matches);
}
} else if (typeof object == 'object') {
for (let key of Object.keys(object)) {
if (key == originalKey) {
if (object[key] == originalValue) {
matches.push(object);
}
} else {
deepSearchByKey(object[key], originalKey, originalValue, matches);
}
}
}
}
return matches;
}
To use:
let result = deepSearchByKey(arrayOrObject, 'key', 'value');
This will return the object containing the matching key and value.

#Iulian Pinzaru's answer was almost exactly what I needed, but it doesn't work if your objects have any null values. This version fixes that.
function deepSearch (object, key, predicate) {
if (object.hasOwnProperty(key) && predicate(key, object[key]) === true) return object
for (let i = 0; i < Object.keys(object).length; i++) {
const nextObject = object[Object.keys(object)[i]];
if (nextObject && typeof nextObject === "object") {
let o = deepSearch(nextObject, key, predicate)
if (o != null) return o
}
}
return null
}

function getPropFromObj(obj, prop) {
let valueToFindByKey;
if (!Array.isArray(obj) && obj !== null && typeof obj === "object") {
if (obj.hasOwnProperty(prop)) {
valueToFindByKey = obj[prop];
console.log(valueToFindByKey);
} else {
let i;
for (i = 0; i < Object.keys(obj).length; i++) {
getPropFromObj(obj[Object.keys(obj)[i]], prop);
}
}
}
return null;
}
const objToInvestigate = {
employeeInformation: {
employees: {
name: "surya",
age: 27,
job: "Frontend Developer",
},
},
};
getPropFromObj(objToInvestigate, "name");
Detecting the key in the deeply nested object.
Finally return the value of the detected key.

Improved answer to take into account circular references within objects.
It also displays the path it took to get there.
In this example, I am searching for an iframe that I know is somewhere within a global object:
const objDone = []
var i = 2
function getObject(theObject, k) {
if (i < 1 || objDone.indexOf(theObject) > -1) return
objDone.push(theObject)
var result = null;
if(theObject instanceof Array) {
for(var i = 0; i < theObject.length; i++) {
result = getObject(theObject[i], i);
if (result) {
break;
}
}
}
else
{
for(var prop in theObject) {
if(prop == 'iframe' && theObject[prop]) {
i--;
console.log('iframe', theObject[prop])
return theObject[prop]
}
if(theObject[prop] instanceof Object || theObject[prop] instanceof Array) {
result = getObject(theObject[prop], prop);
if (result) {
break;
}
}
}
}
if (result) console.info(k)
return result;
}
Running the following:
getObject(reader, 'reader')
gave the following output and the iframe element in the end:
iframe // (The Dom Element)
_views
views
manager
rendition
book
reader
NOTE: The path is in reverse order reader.book.rendition.manager.views._views.iframe

I'd like to suggest an amendment to Zach/RegularMike's answer (but don't have the "reputation" to be able to comment!). I found there solution a very useful basis, but suffered in my application because if there are strings within arrays it would recursively call the function for every character in the string (which caused IE11 & Edge browsers to fail with "out of stack space" errors). My simple optimization was to add the same test used in the "object" clause recursive call to the one in the "array" clause:
if (arrayElem instanceof Object || arrayElem instanceof Array) {
Thus my full code (which is now looking for all instances of a particular key, so slightly different to the original requirement) is:
// Get all instances of specified property deep within supplied object
function getPropsInObject(theObject, targetProp) {
var result = [];
if (theObject instanceof Array) {
for (var i = 0; i < theObject.length; i++) {
var arrayElem = theObject[i];
if (arrayElem instanceof Object || arrayElem instanceof Array) {
result = result.concat(getPropsInObject(arrayElem, targetProp));
}
}
} else {
for (var prop in theObject) {
var objProp = theObject[prop];
if (prop == targetProp) {
return theObject[prop];
}
if (objProp instanceof Object || objProp instanceof Array) {
result = result.concat(getPropsInObject(objProp, targetProp));
}
}
}
return result;
}

Some time ago I have made a small lib find-and, which is available on npm, for working with nested objects in a lodash manner. There's the returnFound function which returns the found object, or an object array if there's more than one object found.
E.g.,
const findAnd = require('find-and');
const a = [
{
'title': "some title",
'channel_id':'123we',
'options': [
{
'channel_id':'abc',
'image':'http://asdasd.com/all-inclusive-block-img.jpg',
'title':'All-Inclusive',
'options':[
{
'channel_id':'dsa2',
'title':'Some Recommends',
'options':[
{
'image':'http://www.asdasd.com',
'title':'Sandals',
'id':'1',
'content':{},
},
],
},
],
},
],
},
];
findAnd.returnFound(a, {id: '1'});
returns
{
'image':'http://www.asdasd.com',
'title':'Sandals',
'id':'1',
'content':{},
}

function getPath(obj, path, index = 0) {
const nestedKeys = path.split('.')
const selectedKey = nestedKeys[index]
if (index === nestedKeys.length - 1) {
return obj[selectedKey]
}
if (!obj.hasOwnProperty(selectedKey)) {
return {}
}
const nextObj = obj[selectedKey]
return Utils.hasPath(nextObj, path, index + 1)
}
You're welcome
By: Gorillaz

This function (main()) allows you to get all objects within a JSON whose key is user-defined. Here is an example:
function main(obj = {}, property) {
const views = [];
function traverse(o) {
for (var i in o) {
if (i === property) views.push(o[i]);
if (!!o[i] && typeof(o[i]) == "object") traverse(o[i]);
}
}
traverse(obj);
return views;
}
const obj = {
id: 'id at level 1',
level2: {
id: 'id at level 2',
level3: {
id: 'id at level 3',
level4: {
level5: {
id: 'id at level 5'
}
}
}
},
text: ''
}
console.log(main(obj, 'id'));

If you're already using Underscore, use _.find()
_.find(yourList, function (item) {
return item.id === 1;
});

Convert returned JSON Object Properties to (lower first) camelCase

I have JSON returned from an API like so:
Contacts: [{ GivenName: "Matt", FamilyName: "Berry" }]
To keep this consistent with my code style (camelCase - lower case first letter) I want to transform the array to produce the following:
contacts: [{ givenName: "Matt", familyName: "Berry" }]
What's the easiest/best way to do this? Create a new Contact object and iterate over all the contacts in the returned array?
var jsonContacts = json["Contacts"],
contacts= [];
_.each(jsonContacts , function(item){
var contact = new Contact( item.GivenName, item.FamilyName );
contacts.push(contact);
});
or can I map the original array or transform it somehow?

If you would use lodash instead of underscore, this would do:
_.mapKeys(obj, (v, k) => _.camelCase(k))
This would convert both TitleCase and snake_case to camelCase. Note that it is not recursive though.

Here's a reliable, recursive function that will properly camelCase all of a JavaScript object's properties:
function toCamel(o) {
var newO, origKey, newKey, value
if (o instanceof Array) {
return o.map(function(value) {
if (typeof value === "object") {
value = toCamel(value)
}
return value
})
} else {
newO = {}
for (origKey in o) {
if (o.hasOwnProperty(origKey)) {
newKey = (origKey.charAt(0).toLowerCase() + origKey.slice(1) || origKey).toString()
value = o[origKey]
if (value instanceof Array || (value !== null && value.constructor === Object)) {
value = toCamel(value)
}
newO[newKey] = value
}
}
}
return newO
}
Test:
var obj = {
'FirstName': 'John',
'LastName': 'Smith',
'BirthDate': new Date(),
'ArrayTest': ['one', 'TWO', 3],
'ThisKey': {
'This-Sub-Key': 42
}
}
console.log(JSON.stringify(toCamel(obj)))
Output:
{
"firstName":"John",
"lastName":"Smith",
"birthDate":"2017-02-13T19:02:09.708Z",
"arrayTest": [
"one",
"TWO",
3
],
"thisKey":{
"this-Sub-Key":42
}
}

You can do this with this recursive function (with lodash and ES6):
import { camelCase } from 'lodash';
const camelizeKeys = (obj) => {
if (Array.isArray(obj)) {
return obj.map(v => camelizeKeys(v));
} else if (obj != null && obj.constructor === Object) {
return Object.keys(obj).reduce(
(result, key) => ({
...result,
[camelCase(key)]: camelizeKeys(obj[key]),
}),
{},
);
}
return obj;
};
Test:
const obj = {
'FirstName': 'John',
'LastName': 'Smith',
'BirthDate': new Date(),
'ArrayTest': ['one', 'TWO', 3],
'ThisKey': {
'This-Sub-Key': 42
}
}
console.log(JSON.stringify(camelizeKeys(obj)))
Output:
{
"firstName": "John",
"lastName": "Smith",
"birthDate": "2018-05-31T09:03:57.844Z",
"arrayTest":[
"one",
"TWO",
3
],
"thisKey":{
"thisSubKey": 42
}
}

To change a plain object's keys from snake_case to camelCase recursively try the following
(which uses Lodash):
function objectKeysToCamelCase(snake_case_object) {
var camelCaseObject = {};
_.forEach(
snake_case_object,
function(value, key) {
if (_.isPlainObject(value) || _.isArray(value)) { // checks that a value is a plain object or an array - for recursive key conversion
value = objectKeysToCamelCase(value); // recursively update keys of any values that are also objects
}
camelCaseObject[_.camelCase(key)] = value;
}
)
return camelCaseObject;
};
test in this PLUNKER
Note: also works recursively for objects within arrays

Using lodash and ES6, this will replace all keys recursively to camelcase:
const camelCaseKeys = (obj) => {
if (!_.isObject(obj)) {
return obj;
} else if (_.isArray(obj)) {
return obj.map((v) => camelCaseKeys(v));
}
return _.reduce(obj, (r, v, k) => {
return {
...r,
[_.camelCase(k)]: camelCaseKeys(v)
};
}, {});
};

Just use humps
humps.camelize('hello_world');
humps.camelizeKeys(object, options); // will work through entire object
https://www.npmjs.com/package/humps

This is a great use case for axios interceptors
Basically, define a client class and attach a before/after interceptor that converts the request/response data.
export default class Client {
get(url, data, successCB, catchCB) {
return this._perform('get', url, data, successCB, catchCB);
}
post(url, data, successCB, catchCB) {
return this._perform('post', url, data, successCB, catchCB);
}
_perform(method, url, data, successCB, catchCB) {
// https://github.com/axios/axios#interceptors
// Add a response interceptor
axios.interceptors.response.use((response) => {
response.data = toCamelCase(response.data);
return response;
}, (error) => {
error.data = toCamelCase(error.data);
return Promise.reject(error);
});
// Add a request interceptor
axios.interceptors.request.use((config) => {
config.data = toSnakeCase(config.data);
return config;
}, (error) => {
return Promise.reject(error);
});
return axios({
method: method,
url: API_URL + url,
data: data,
headers: {
'Content-Type': 'application/json',
},
}).then(successCB).catch(catchCB)
}
}
Here's a gist with a longer example using React/axios.

there's a nice npm module for this..
https://www.npmjs.com/package/camelcase-keys
npm install camelcase-keys
const camelcaseKeys = require( "camelcase-keys" );
camelcaseKeys( { Contacts: [ { GivenName: "Matt", FamilyName: "Berry" } ] }, { deep: true } );
will return...
{ contacts: [ { givenName: "Matt", familyName: "Berry" } ] }

This solution based on the plain js solution above, uses loadash and Keeps an array if passed as a parameter and Only change the Keys
function camelCaseObject(o) {
let newO, origKey, value
if (o instanceof Array) {
newO = []
for (origKey in o) {
value = o[origKey]
if (typeof value === 'object') {
value = camelCaseObject(value)
}
newO.push(value)
}
} else {
newO = {}
for (origKey in o) {
if (o.hasOwnProperty(origKey)) {
newO[_.camelCase(origKey)] = o[origKey]
}
}
}
return newO
}
// Example
const obj = [
{'my_key': 'value'},
{'Another_Key':'anotherValue'},
{'array_key':
[{'me_too':2}]
}
]
console.log(camelCaseObject(obj))
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

Using lodash, you can do it like this:
export const toCamelCase = obj => {
return _.reduce(obj, (result, value, key) => {
const finalValue = _.isPlainObject(value) || _.isArray(value) ? toCamelCase(value) : value;
return { ...result, [_.camelCase(key)]: finalValue };
}, {});
};

Well I took up the challenge and think I figured it out:
var firstToLower = function(str) {
return str.charAt(0).toLowerCase() + str.slice(1);
};
var firstToUpper = function(str) {
return str.charAt(0).toUpperCase() + str.slice(1);
};
var mapToJsObject = function(o) {
var r = {};
$.map(o, function(item, index) {
r[firstToLower(index)] = o[index];
});
return r;
};
var mapFromJsObject = function(o) {
var r = {};
$.map(o, function(item, index) {
r[firstToUpper(index)] = o[index];
});
return r;
};
// Map to
var contacts = [
{
GivenName: "Matt",
FamilyName: "Berry"
},
{
GivenName: "Josh",
FamilyName: "Berry"
},
{
GivenName: "Thomas",
FamilyName: "Berry"
}
];
var mappedContacts = [];
$.map(contacts, function(item) {
var m = mapToJsObject(item);
mappedContacts.push(m);
});
alert(mappedContacts[0].givenName);
// Map from
var unmappedContacts = [];
$.map(mappedContacts, function(item) {
var m = mapFromJsObject(item);
unmappedContacts.push(m);
});
alert(unmappedContacts[0].GivenName);
Property converter (jsfiddle)
The trick is handling the objects as arrays of object properties.

Here's handy library you might wanna try:
https://www.npmjs.com/package/camelize2
You simply need to install it with npm install --save camelize2 and then
const camelize = require('camelize2')
const response = {
Contacts: [{ GivenName: "Matt", FamilyName:"Berry" }]
}
const camelizedResponse = camelize(response)

Solution similar to #brandonscript, but in more ES6-functional way:
const camelCaseString = str => (
(str.charAt(0).toLowerCase() + str.slice(1) || str).toString()
);
const objectToCamelCase = val => {
if (typeof val != 'object' || val === null) {
return val;
}
if (val instanceof Array) {
return val.map(objectToCamelCase);
}
return Object.keys(val)
.filter(prop => val.hasOwnProperty(prop))
.map(prop => ({[camelCaseString(prop)]: objectToCamelCase(val[prop])}))
.reduce((prev, current) => ({...prev, ...current}))
};
// Example:
let converted = objectToCamelCase({UserId: 1, Hobbies: [{Id: 1, Label: "Read"}], Name: "John Doe"});
console.log(converted)

I needed a generic method that accepted an array or object. This is what I'm using (I borrowed KyorCode's firstToLower() implementation):
function convertKeysToCamelCase(obj) {
if (!obj || typeof obj !== "object") return null;
if (obj instanceof Array) {
return $.map(obj, function(value) {
return convertKeysToCamelCase(value);
});
}
var newObj = {};
$.each(obj, function(key, value) {
key = key.charAt(0).toLowerCase() + key.slice(1);
if (typeof value == "object" && !(value instanceof Array)) {
value = convertKeysToCamelCase(value);
}
newObj[key] = value;
});
return newObj;
};
Example calls:
var contact = { GivenName: "Matt", FamilyName:"Berry" };
console.log(convertKeysToCamelCase(contact));
// logs: Object { givenName="Matt", familyName="Berry"}
console.log(convertKeysToCamelCase([contact]));
// logs: [Object { givenName="Matt", familyName="Berry"}]
console.log(convertKeysToCamelCase("string"));
// logs: null
console.log(contact);
// logs: Object { GivenName="Matt", FamilyName="Berry"}

Took the challenge with lodash and some es6+ features
Here is my implementation with the reduce function.
function deeplyToCamelCase(obj) {
return _.reduce(obj, (camelCaseObj, value, key) => {
const convertedDeepValue = _.isPlainObject(value) || _.isArray(value)
? deeplyToCamelCase(value)
: value;
return { ...camelCaseObj, [_.camelCase(key)] : convertedDeepValue };
}, {});
};

Use lodash ...
function isPrimitive (variable) {
return Object(variable) !== variable
}
function toCamel (variable) {
if (isPrimitive(variable)) {
return variable
}
if (_.isArray(variable)) {
return variable.map(el => toCamel(el))
}
const newObj = {}
_.forOwn(variable, (value, key) => newObj[_.camelCase(key)] = toCamel(value))
return newObj
}

This function loop recursively through the object keys and using lodash returns a new object with every field converted to camelCase. It works also with arrays, nested arrays, nested objects.
function deepCamelCase (obj) {
const c = {}
if (typeof obj !== 'object') return obj
_.mapKeys(obj, (v, k) => {
let w = {}
if (typeof v === 'object') {
if (Array.isArray(v)) {
const k = []
for (const i of v) {
k.push(deepCamelCase(i))
}
} else {
_.mapValues(v, (n, m) => {
if (Array.isArray(n)) {
const k = []
for (const i of n) {
k.push(deepCamelCase(i))
}
w[_.camelCase(m)] = k
} else {
w[_.camelCase(m)] = deepCamelCase(n)
}
})
}
} else {
w = v
}
c[_.camelCase(k)] = w
})
return c
}

Updated code using the reference from https://plnkr.co/edit/jtsRo9yU12geH7fkQ0WL?p=preview
This handles the Objects with array with objects inside it too and so on, by keeping arrays as arrays (which you can iterate over using map)
function snakeToCamelCase(snake_case_object){
var camelCaseObject;
if (isPlainObject(snake_case_object)) {
camelCaseObject = {};
}else if(isArray(snake_case_object)){
camelCaseObject = [];
}
forEach(
snake_case_object,
function(value, key) {
if (isPlainObject(value) || isArray(value)) {
value = snakeToCamelCase(value);
}
if (isPlainObject(camelCaseObject)) {
camelCaseObject[camelCase(key)] = value;
}else if(isArray(camelCaseObject)){
camelCaseObject.push(value);
}
}
)
return camelCaseObject;
}

This is my take; more readable and with less nesting than brandoncode's implementation, and with more room for handling edge cases like Date (which isn't handled, by the way) or null:
function convertPropertiesToCamelCase(instance) {
if (instance instanceof Array) {
var result = [];
for (var i = 0; i < instance.length; i++) {
result[i] = convertPropertiesToCamelCase(instance[i]);
}
return result;
}
if (typeof instance != 'object') {
return instance;
}
var result = {};
for (var key in instance) {
if (!instance.hasOwnProperty(key)) {
continue;
}
result[key.charAt(0).toLowerCase() + key.substring(1)] = convertPropertiesToCamelCase(instance[key]);
}
return result;
}

Building on goredwards answer (which didn't handle the array fields correctly)
function objectKeysToCamelCase(snake_case_object) {
let camelCaseObject = {}
_.forEach(
snake_case_object,
function(value, key) {
if (_.isPlainObject(value)) {
value = objectKeysToCamelCase(value)
} else if (_.isArray(value)) {
value = value.map(v => _.isPlainObject(v) ? objectKeysToCamelCase(v) : v)
}
camelCaseObject[_.camelCase(key)] = value
},
)
return camelCaseObject
}

here is code I found for it, not fully tested though, but worth sharing.
It is far more readable than other answers, not sure about performance.
test it http://jsfiddle.net/ms734bqn/1/
const toCamel = (s) => {
return s.replace(/([-_][a-z])/ig, ($1) => {
return $1.toUpperCase()
.replace('-', '')
.replace('_', '');
});
};
const isArray = function (a) {
return Array.isArray(a);
};
const isObject = function (o) {
return o === Object(o) && !isArray(o) && typeof o !== 'function';
};
const keysToCamel = function (o) {
if (isObject(o)) {
const n = {};
Object.keys(o)
.forEach((k) => {
n[toCamel(k)] = keysToCamel(o[k]);
});
return n;
} else if (isArray(o)) {
return o.map((i) => {
return keysToCamel(i);
});
}
return o;
};

Pure JavaScript, shoud work fine
function convertKeysToCamelCase(object) {
if(object === undefined || object === null || typeof object !== "object") {
return object;
} else {
if(Array.isArray(object)) {
return object.map(item => convertKeysToCamelCase(item));
} else {
return Object.entries(object).reduce((result, [key, value]) => {
result[key.charAt(0).toLowerCase() + key.slice(1)] = convertKeysToCamelCase(value);
return result;
}, {});
}
}
}

you can do this simply by using json-case-convertor
const jcc = require('json-case-convertor')
const jsonData = ''//you json data to convert
const camelCasedJson = jcc.camelCaseKeys(jsonData) //Convert all the keys of object to snake case
This will handle all cascaded object as well

Convert object keys to camelCase with deep.
import _ from 'lodash';
export function objectKeysToCamelCase(entity) {
if (!_.isObject(entity)) return entity;
let result;
result = _.mapKeys(entity, (value, key) => _.camelCase(key));
result = _.mapValues(result, (value) => objectKeysToCamelCase(value));
return result;
}