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How to deep remove falsey values and empty objects from an object using lodash

How to deep remove all falsey values and empty objects using lodash ?
f.e. I want my object :
{ a:undefined, b:2, c:4, d:undefined , e:{ f:{} , g:null } }
to become:
{ b:2, c:4 };

var test = {
a: undefined,
b: 2,
c: 4,
d: undefined,
e: {
f: {},
g: null
}
};
function clean(obj) {
for (var propName in obj) {
if (_.isObject(obj[propName])) {
clean(obj[propName]);
}
if (obj[propName] === null || obj[propName] === undefined || _.isObject(obj[propName]) && _.isEmpty(obj[propName])) {
delete obj[propName];
}
}
}
clean(test);
console.log(test);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.20/lodash.min.js"></script>

You could get the properties to delete and get a clean object. This approach mutates to original object.
function clean(value) {
if (value === null || value === undefined) return true;
if (typeof value !== 'object') return false;
if (Array.isArray(value)) {
let i = value.length;
while (i--) if (clean(value[i])) value.splice(i, 1);
return !value.length;
}
Object
.keys(value)
.filter(k => clean(value[k]))
.forEach(Reflect.deleteProperty.bind(null, value));
return !Object.keys(value).length;
}
const
object = { a: undefined, b: 2, c: 4, d: undefined, e: { f: {}, g: null } , h: [], i: [1, []], j: [[[], []]] };
clean(object);
console.log(object);

The question is pretty vague and doesn't specify whether the original structure may or may not be mutated. There is also nothing in there about arrays.
This answer assumes that you don't want to mutate the original data structure and that "deep" also means to go through all array elements. If the object or array results in an empty instance the corresponding key will be removed.
function deepCompact(collection) {
const add = _.isArray(collection)
? (collection, key, value) => collection.push(value)
: (collection, key, value) => collection[key] = value;
return _.transform(collection, (collection, value, key) => {
if (_.isObject(value)) {
value = deepCompact(value);
if (_.isEmpty(value)) return;
} else {
if (!value) return;
}
add(collection, key, value);
});
}
const data1 = {a: undefined, b: 2, c: 4, d: undefined, e: {f: {} , g: null}};
console.log(deepCompact(data1));
const data2 = [{a: 0, b: 2}, false, {c: [{d: null}]}, {e: [{f: 1}]}];
console.log(deepCompact(data2));
<script src="https://cdn.jsdelivr.net/npm/lodash#4.17.20/lodash.min.js"></script>
transform is comparable to reduce, however the first callback parameter is locked to the provided or default accumulator. This means you don't have to return the accumulator from the callback. The default accumulator of transform also differs from reduce. reduce uses the first element as the initial value, whereas transform uses a new object with the same prototype as the provided collection as the default value.

Given an object how can I get the name used to describe it?

I have a JSON object(mainObj) which in turn has objects (say obj1, obj2, obj3). What I am trying to achieve is when I check for a condition iterating through every obj in the mainObj and if it holds true, I want to add only the name of that obj in an array of String. Something like,
for(obj in mainObj){
if(obj holds condition){
add the descriptor of the obj (in string format) to an array (not the entire obj)
}

You can use Object.keys() to iterate over your object keys, then use Array.filter() to filter the keys, here I am checking if the inner objects have a property show and if this property is truthy:
const mainObj = {
obj1: { show: true, a: 1 },
obj2: { show: false, a: 2 },
obj3: { a: 3 },
obj4: { show: true, b: 1 }
};
const result = Object.keys(mainObj).filter(key => mainObj[key].show);
console.log(result);
If you want to use a for-in loop, you have to make sure the property is part of the object and is not inherited from its protype chain using Object.hasOwnProperty():
const mainObj = {
obj1: { show: true, a: 1 },
obj2: { show: false, a: 2 },
obj3: { a: 3 },
obj4: { show: true, b: 1 }
};
const result = [];
for (const prop in mainObj) {
if (mainObj.hasOwnProperty(prop) && mainObj[prop].show) {
result.push(prop);
}
}
console.log(result);

how to transform an object to an array based on key/value?

I have an object with few properties true/false, I need to return an array with only the property name with true.
I have tried Object.entries but not sure how to create an array now.
const inputs = {
a: true,
b: true,
c: false
}
// result should be ['a','b']
// i have tried so far this one with no success
// const result = Object.entries(inputs).map((x, idx) => console.log(x))

Object.keys(inputs).filter(key => inputs[key])

Use my JSFiddle for the code.
Use the filter array method, described by MDN as
creates a new array with all elements that pass the test implemented by the provided function
Call it on the Object.keys, a built in array for objects:
returns an array of a given object's property names
Source: Object.keys()
So, to put it together, it would look like
const inputs = {
a: true,
b: true,
c: false
}
console.log(inputs); // Output: {a: true, b: true, c: false}
const arr = Object.keys(inputs).filter(keyName => inputs[keyName]);
console.log(arr); // Output: ["a", "b"]

For give only keys of object use filter:
Like this:
const inputs = {
a: true,
b: true,
c: false
};
var true_inputs = Object.keys(inputs).filter(key => inputs[key]);
console.log(true_inputs);
Or Jquery map:
const inputs = {
a: true,
b: true,
c: false
};
var true_inputs = $.map(inputs, function(n, i) { if(n) return i });
console.log(true_inputs);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
For to get the whole object use for .. in:
Like this:
const inputs = {
a: true,
b: true,
c: false
};
var true_inputs = {};
for(var key in inputs){
if(inputs[key])
true_inputs[key]=inputs[key];
}
console.log(inputs);
console.log(true_inputs);

Change one property of object

I need to loop through object and change exactly one of its non-true properties to true.
var object = {a: true, b: false, c: false, d: false}
function changeOne(object) {
for(var i in object) {
if(object[i] !== true) {
object[i] = true;
break;
}
}
}
This seems like a really bad way to go about this. Is there a better way?

Your code is actually fine just that the key order of objects is not defined, so your code might set b or c or d depending on the browsers engine (very unlikely that its not b but you never know...), so you should give an order by yourself:
function changeOne(object) {
for(var key of ["a", "b", "c", "d"]) {
if(object[key] !== true) {
object[key] = true;
break;
}
}
}
If you meant "better" in the sense of "shorter":
const changeOne = obj => ["a", "b", "c", "d"].some(key => (obj[key] !== true) && (obj[key] = true));

You could take the entries of the object and use Array#every for a short circuit after a changed property.
function setToTrue(object) {
Object.entries(object).every(([k, v]) => v || !(object[k] = true));
return object;
}
var object = { a: true, b: false, c: false, d: false };
console.log(setToTrue(object));
console.log(setToTrue(object));
console.log(setToTrue(object));
.as-console-wrapper { max-height: 100% !important; top: 0; }

You can iterate the keys and modify the first one that has a false value:
for (let key of Object.keys(obj)) {
if (obj[key] !== true) {
obj[key] = true;
break;
}
}
OUTPUT
{ a: true, b: true, c: false, d: false }
Explanation
Object.keys(obj) will get an array of properties defined on the object itself, while var i in object will return additional properties which are part of the prototype. An alternative would be to add a check for obj.hasOwnProperty(key).

How to remove undefined and null values from an object using lodash?

I have a Javascript object like:
var my_object = { a:undefined, b:2, c:4, d:undefined };
How to remove all the undefined properties? False attributes should stay.

You can simply chain _.omit() with _.isUndefined and _.isNull compositions, and get the result with lazy evaluation.
Demo
var result = _(my_object).omit(_.isUndefined).omit(_.isNull).value();
Update March 14, 2016:
As mentioned by dylants in the comment section, you should use the _.omitBy() function since it uses a predicate instead of a property. You should use this for lodash version 4.0.0 and above.
DEMO
var result = _(my_object).omitBy(_.isUndefined).omitBy(_.isNull).value();
Update June 1, 2016:
As commented by Max Truxa, lodash already provided an alternative _.isNil, which checks for both null and undefined:
var result = _.omitBy(my_object, _.isNil);

If you want to remove all falsey values then the most compact way is:
For Lodash 4.x and later:
_.pickBy({ a: null, b: 1, c: undefined }, _.identity);
>> Object {b: 1}
For legacy Lodash 3.x:
_.pick(obj, _.identity);
_.pick({ a: null, b: 1, c: undefined }, _.identity);
>> Object {b: 1}

The correct answer is:
_.omitBy({ a: null, b: 1, c: undefined, d: false }, _.isNil)
That results in:
{b: 1, d: false}
The alternative given here by other people:
_.pickBy({ a: null, b: 1, c: undefined, d: false }, _.identity);
Will remove also false values which is not desired here.

if you are using lodash, you can use _.compact(array) to remove all falsely values from an array.
_.compact([0, 1, false, 2, '', 3]);
// => [1, 2, 3]
https://lodash.com/docs/4.17.4#compact

Just:
_.omit(my_object, _.isUndefined)
The above doesn't take in account null values, as they are missing from the original example and mentioned only in the subject, but I leave it as it is elegant and might have its uses.
Here is the complete example, less concise, but more complete.
var obj = { a: undefined, b: 2, c: 4, d: undefined, e: null, f: false, g: '', h: 0 };
console.log(_.omit(obj, function(v) { return _.isUndefined(v) || _.isNull(v); }));

To complete the other answers, in lodash 4 to ignore only undefined and null (And not properties like false) you can use a predicate in _.pickBy:
_.pickBy(obj, v !== null && v !== undefined)
Example below :
const obj = { a: undefined, b: 123, c: true, d: false, e: null};
const filteredObject = _.pickBy(obj, v => v !== null && v !== undefined);
console.log = (obj) => document.write(JSON.stringify(filteredObject, null, 2));
console.log(filteredObject);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.js"></script>

According to lodash docs:
_.compact(_.map(array, fn))
Also you can filter out all nulls

For deep nested object you can use my snippet for lodash > 4
const removeObjectsWithNull = (obj) => {
return _(obj)
.pickBy(_.isObject) // get only objects
.mapValues(removeObjectsWithNull) // call only for values as objects
.assign(_.omitBy(obj, _.isObject)) // save back result that is not object
.omitBy(_.isNil) // remove null and undefined from object
.value(); // get value
};

with pure JavaScript: (although Object.entries is ES7, Object.assign is ES6; but equivalent ES5 uses Object.keys only should be also doable); also notice v != null checks for both null and undefined;
> var d = { a:undefined, b:2, c:0, d:undefined, e: null, f: 0.3, s: "", t: false };
undefined
> Object.entries(d)
.filter(([ k, v ]) => (v != null))
.reduce((acc, [k, v]) => Object.assign(acc, {[k]: v}), {})
{ b: 2, c: 0, f: 0.3, s: '', t: false }
Edit: this below is the version with ES5 Object.keys only: but generally with ES7 in Node v8 is pretty much enjoyable ;-)
> Object.keys(d)
.filter(function(k) { return d[k] != null; })
.reduce(function(acc, k) { acc[k] = d[k]; return acc; }, {});
{ b: 2, c: 0, f: 0.3, s: '', t: false }
Update in October 2017: with Node v8 (since v8.3 or so) now it has object spreading construct:
> var d = { a:undefined, b:2, c:0, d:undefined,
e: null, f: -0.0, s: "", t: false, inf: +Infinity, nan: NaN };
undefined
> Object.entries(d)
.filter(([ k, v ]) => (v != null))
.reduce((acc, [k, v]) => ({...acc, [k]: v}), {})
{ b: 2, c: 0, f: -0, s: '', t: false, inf: Infinity, nan: NaN }
or within one reduce only:
> Object.entries(d)
.reduce((acc, [k, v]) => (v==null ? acc : {...acc, [k]: v}), {})
{ b: 2, c: 0, f: -0, s: '', t: false, inf: Infinity, nan: NaN }
Update: someone want recursive? isn't that hard either, just need an additional check of isObject, and recursively call itself:
> function isObject(o) {
return Object.prototype.toString.call(o) === "[object Object]"; }
undefined
> function dropNullUndefined(d) {
return Object.entries(d)
.reduce((acc, [k, v]) => (
v == null ? acc :
{...acc, [k]: (isObject(v) ? dropNullUndefined(v) : v) }
), {});
}
> dropNullUndefined({a: 3, b:null})
{ a: 3 }
> dropNullUndefined({a: 3, b:null, c: { d: 0, e: undefined }})
{ a: 3, c: { d: 0 } }
my conclusion: if pure Javascript can do, I would avoid any third party library dependencies:

To remove undefined, null, and empty string from object
_.omitBy(object, (v) => _.isUndefined(v) || _.isNull(v) || v === '');

I encountered a similar problem with removing undefined from an object (deeply), and found that if you are OK to convert your plain old object and use JSON, a quick and dirty helper function would look like this:
function stripUndefined(obj) {
return JSON.parse(JSON.stringify(obj));
}
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#Description
"...If undefined, a function, or a symbol is encountered during conversion it is either omitted (when it is found in an object) or censored to null (when it is found in an array)."

Since some of you might have arrived at the question looking to specifically removing only undefined, you can use:
a combination of Lodash methods
_.omitBy(object, _.isUndefined)
the rundef package, which removes only undefined properties
rundef(object)
If you need to recursively remove undefined properties, the rundef package also has a recursive option.
rundef(object, false, true);
See the documentation for more details.

Here's the lodash approach I'd take:
_(my_object)
.pairs()
.reject(function(item) {
return _.isUndefined(item[1]) ||
_.isNull(item[1]);
})
.zipObject()
.value()
The pairs() function turns the input object into an array of key/value arrays. You do this so that it's easier to use reject() to eliminate undefined and null values. After, you're left with pairs that weren't rejected, and these are input for zipObject(), which reconstructs your object for you.

Taking in account that undefined == null we can write as follows:
let collection = {
a: undefined,
b: 2,
c: 4,
d: null,
}
console.log(_.omit(collection, it => it == null))
// -> { b: 2, c: 4 }
JSBin example

I like using _.pickBy, because you have full control over what you are removing:
var person = {"name":"bill","age":21,"sex":undefined,"height":null};
var cleanPerson = _.pickBy(person, function(value, key) {
return !(value === undefined || value === null);
});
Source: https://www.codegrepper.com/?search_term=lodash+remove+undefined+values+from+object

You can also use Object.entries with Array.prototype.filter.
const omitNullish = (object) =>
Object.fromEntries(
Object.entries(object).filter(([, value]) => value != null)
)
omitNullish({ a: null, b: 1, c: undefined, d: false, e: 0 }) // { b: 1, d: false, e: 0}
If you want to use lodash, they are removing omit from v5 so an alternative is to use fp/pickBy along with isNil and negate.
import pickBy from 'lodash/fp/pickBy'
import isNil from 'lodash/isNil';
import negate from 'lodash/negate';
const omitNullish = pickBy(negate(isNil))
omitNullish({ a: null, b: 1, c: undefined, d: false, e: 0 }) // { b: 1, d: false, e: 0}

pickBy uses identity by default:
_.pickBy({ a: null, b: 1, c: undefined, d: false });

With lodash (or underscore) You may do
var my_object = { a:undefined, b:2, c:4, d:undefined, e:null };
var passedKeys = _.reject(Object.keys(my_object), function(key){ return _.isUndefined(my_object[key]) || _.isNull(my_object[key]) })
newObject = {};
_.each(passedKeys, function(key){
newObject[key] = my_object[key];
});
Otherwise, with vanilla JavaScript, you can do
var my_object = { a:undefined, b:2, c:4, d:undefined };
var new_object = {};
Object.keys(my_object).forEach(function(key){
if (typeof my_object[key] != 'undefined' && my_object[key]!=null){
new_object[key] = my_object[key];
}
});
Not to use a falsey test, because not only "undefined" or "null" will be rejected, also is other falsey value like "false", "0", empty string, {}. Thus, just to make it simple and understandable, I opted to use explicit comparison as coded above.

To omit all falsey values but keep the boolean primitives this solution helps.
_.omitBy(fields, v => (_.isBoolean(v)||_.isFinite(v)) ? false : _.isEmpty(v));
let fields = {
str: 'CAD',
numberStr: '123',
number : 123,
boolStrT: 'true',
boolStrF: 'false',
boolFalse : false,
boolTrue : true,
undef: undefined,
nul: null,
emptyStr: '',
array: [1,2,3],
emptyArr: []
};
let nobj = _.omitBy(fields, v => (_.isBoolean(v)||_.isFinite(v)) ? false : _.isEmpty(v));
console.log(nobj);
<script src="https://cdn.jsdelivr.net/npm/lodash#4.17.11/lodash.min.js"></script>

Shortest way (lodash v4):
_.pickBy(my_object)

If you don't want to remove false values. Here is an example:
obj = {
"a": null,
"c": undefined,
"d": "a",
"e": false,
"f": true
}
_.pickBy(obj, x => x === false || x)
> {
"d": "a",
"e": false,
"f": true
}

You can use lodash to remove null and undefined objects , but you should konw what lodash method you need to use, many dev uses isNil to remove the Null and undefined objects , but this function not remove the empty objects (' ')
you can use isEmpty to remove Null , Undefined and
import pickBy from 'lodash/fp/pickBy'
import negate from 'lodash/negate';
import isEmpty from 'lodash/isEmpty';
const omitNullish = pickBy(negate(isEmpty));
addressObject = {
"a": null,
"c": undefined,
"d": "",
"e": "test1",
"f": "test2
}
const notNullObjects = omitNullish(addressObject);
console.log(notNullObjects);
you will have this object : {
"e": "test1",
"f": "test2
}

var my_object = { a:undefined, b:2, c:4, d:undefined };
var newObject = _.reject(my_collection, function(val){ return _.isUndefined(val) })
//--> newCollection = { b: 2, c: 4 }

I would use underscore and take care of empty strings too:
var my_object = { a:undefined, b:2, c:4, d:undefined, k: null, p: false, s: '', z: 0 };
var result =_.omit(my_object, function(value) {
return _.isUndefined(value) || _.isNull(value) || value === '';
});
console.log(result); //Object {b: 2, c: 4, p: false, z: 0}
jsbin.

For deep nested object and arrays. and exclude empty values from string and NaN
function isBlank(value) {
return _.isEmpty(value) && !_.isNumber(value) || _.isNaN(value);
}
var removeObjectsWithNull = (obj) => {
return _(obj).pickBy(_.isObject)
.mapValues(removeObjectsWithNull)
.assign(_.omitBy(obj, _.isObject))
.assign(_.omitBy(obj, _.isArray))
.omitBy(_.isNil).omitBy(isBlank)
.value();
}
var obj = {
teste: undefined,
nullV: null,
x: 10,
name: 'Maria Sophia Moura',
a: null,
b: '',
c: {
a: [{
n: 'Gleidson',
i: 248
}, {
t: 'Marta'
}],
g: 'Teste',
eager: {
p: 'Palavra'
}
}
}
removeObjectsWithNull(obj)
result:
{
"c": {
"a": [
{
"n": "Gleidson",
"i": 248
},
{
"t": "Marta"
}
],
"g": "Teste",
"eager": {
"p": "Palavra"
}
},
"x": 10,
"name": "Maria Sophia Moura"
}

For those of you getting here looking to remove from an array of objects and using lodash you can do something like this:
const objects = [{ a: 'string', b: false, c: 'string', d: undefined }]
const result = objects.map(({ a, b, c, d }) => _.pickBy({ a,b,c,d }, _.identity))
// [{ a: 'string', c: 'string' }]
Note: You don't have to destruct if you don't want to.

I was able to do this in deep objects that include arrays with just one lodash function, transform.
Note that the double-unequal (!= null) is intentional as it will also match undefined, as is the typeof 'object' check as it will match both object and array.
This is for use with plain data objects only that don't contain classes.
const cloneDeepSanitized = (obj) =>
Array.isArray(obj)
? obj.filter((entry) => entry != null).map(cloneDeepSanitized)
: transform(
obj,
(result, val, key) => {
if (val != null) {
result[key] =
typeof val === 'object' ? cloneDeepSanitized(val) : val;
}
},
{},
);