How to get an array of just the keys that have values attached in Javascript?

Question

So lets say I have an object like this:

myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
}

And I want an array of the keys, but only if the have a value. i.e. if they're undefined or empty string, I don't want them included in the array.

Currently I'm using Object.keys(myObject) but this gets all the keys including those that are undefined, false or nullable value.

I completely understand I can likely write my own version of the keys method from Object, but I'm wondering if there's an easier way than that.

keys() does what it says, so you'll want a custom filter instead, as someone already wrote in less than a minute. — YellowAfterlife
– YellowAfterlife, Commented Feb 19, 2021 at 16:11

CertainPerformance · Accepted Answer · 2021-02-19 16:10:29Z

2

Filter the entries by whether the key portion of the entry is truthy, then map to the keys:

const myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
};

const keys = Object.entries(myObject)
  .filter(([, val]) => val)
  .map(([key]) => key);
console.log(keys);

answered Feb 19, 2021 at 16:10

CertainPerformance

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2 Comments

Salmin Skenderovic Over a year ago

If they are only interested in the keys - Object.keys has one less iteration

sbrevolution5 Over a year ago

This one definitley worked, but oddly enough the others where Object.keys was used kept returning an empty array for some reason.

Salmin Skenderovic · Accepted Answer · 2021-02-19 16:12:43Z

2

You only need to use Array.filter() to remove the keys that have nullable results

const myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
};

const keys = Object.keys(myObject)
  .filter(key => myObject[key])
console.log(keys);

answered Feb 19, 2021 at 16:12

Salmin Skenderovic

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Comments

Daniel Beck · Accepted Answer · 2021-02-19 16:13:36Z

2

If all you care about are the truthy keys you can use a somewhat simpler filter than above:

myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
}

truthyKeys = Object
     .keys(myObject) // array of all keys
     .filter(k => myObject[k]) // filter out ones with falsy values

console.log(truthyKeys)

answered Feb 19, 2021 at 16:13

Daniel Beck

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Comments

Cory Harper · Accepted Answer · 2021-02-19 16:14:08Z

2

const myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
};

const keys = Object.keys(myObject).filter(key => myObject[key]);

This will also cut out other falsy values however, such as 0, NaN, null, false. If you very specifically are guarding against empty strings and undefined:

const myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
};

const keys = Object.keys(myObject)
  .filter(key => myObject[key] !== '' && myObject[key] !== undefined);

answered Feb 19, 2021 at 16:14

Cory Harper

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Comments

sundeep sharma · Accepted Answer · 2021-02-19 17:18:55Z

1

try it.

myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
}

let x= Object.entries(myObject);
for(i=0;i<x.length;i++){
if(x[i][1]!==undefined&&x[i][1]!==""){
console.log(x[i][0])}
}

answered Feb 19, 2021 at 17:18

sundeep sharma

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Comments

Raycas · Accepted Answer · 2021-02-19 16:14:57Z

0

I don't know if there is another way but you can try something like this

myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
}

const getValue = (obj) => {
    const array = [];
  for (const [key, value] of Object.entries(obj)) {
    if(value){
    array.push(key);
    }
  }
  return array;
}


console.log(getValue(myObject));

answered Feb 19, 2021 at 16:14

Raycas

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Comments

Ran Turner · Accepted Answer · 2021-02-19 16:31:28Z

0

let objectWithTruthyKeys = Object.keys(myObject).filter(i => myObject[i]);

Explanation:

Object.keys will get all the keys of the property (including the ones that contain falsy values).
The filter will go through each key in myObject (represented by i). the condition will be true only if the value is truthy, hence, filtering out the keys which contain falsy values.

edited Feb 19, 2021 at 16:31

answered Feb 19, 2021 at 16:23

Ran Turner

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Comments

Leandro Benedet Garcia · Accepted Answer · 2021-02-19 16:40:07Z

0

There's a couple ways to do that. You could use filter:

const myObject = {
    key1: "foo",
    key2: "",
    key3: "bar",
    key4: "foobar",
    key5: undefined
}
        
var keysWithValues = Object.keys(myObject).filter(key => myObject[key]);

console.log(keysWithValues);

Or a for loop:

const myObject = {
  key1: "foo",
  key2: "",
  key3: "bar",
  key4: "foobar",
  key5: undefined
}

var keysWithValues = [];

for (const [key, value] of Object.entries(myObject)) {
  if (value) {
    keysWithValues.push(key);
  }
}
console.log(keysWithValues);

You could also be fancy and extend Object by creating a class. But I believe that would be overkill :D

answered Feb 19, 2021 at 16:40

Leandro Benedet Garcia

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