How to find value in JSON object array?

Question

I have a JSON object like this

myObj = {
"knowncount": [{
    "id": "planet",
    "knownCount": 8,
    "updateDate": "24/08/2006",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/planet"
}, {
    "id": "dwarfPlanet",
    "knownCount": 5,
    "updateDate": "24/08/2006",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/dwarfPlanet"
}, {
    "id": "asteroid",
    "knownCount": 1027022,
    "updateDate": "11/11/2020",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/asteroid"
}, {
    "id": "comet",
    "knownCount": 3690,
    "updateDate": "11/11/2020",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/comet"
}]}

How can I search my object to find where the key is 'id' and then print its value for knownCount?

Example. If 'id' == 'planet'

// 8

I've tried to covert to array to use array functions like array.find() but this doesn't seem to work. I check type with typeof and continue to get type object. What is the correct way to change to array or is there a comparable way to do this with objects or must I iterate over the object and create a set or something similar?

Does this answer your question? Find object by property in JSON array — Calvin Nunes
– Calvin Nunes, Commented Jan 26, 2021 at 21:14
Does this answer your question? Find object by id in an array of JavaScript objects — Calvin Nunes
– Calvin Nunes, Commented Jan 26, 2021 at 21:15
Does this answer your question? Find object by id in an array of JavaScript objects — evolutionxbox
– evolutionxbox, Commented Jan 26, 2021 at 21:17
myObj.knowncount.find(({id}) => id === 'planet')?.knownCount — Yevhen Horbunkov
– Yevhen Horbunkov, Commented Jan 26, 2021 at 21:17

Meroz · Accepted Answer · 2021-01-26 21:22:12Z

0

myObj
 .knowncount
 .find(({ id }) => id === 'planet')
 .knownCount;

answered Jan 26, 2021 at 21:22

Meroz

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1 Comment

Yevhen Horbunkov Over a year ago

If desired id value is never met, this code will throw Referrence Error

Israel Bessa · Accepted Answer · 2021-01-26 21:35:14Z

0

Try it

const res = myObj.knowncount.find(el => el.id === 'planet')?.knownCount || 'Planet not found';
console.log(res);

You can't use finddirectly on the myObj because it's an Object, and not an Array.

myObj = {
"knowncount": [{
    "id": "planet",
    "knownCount": 8,
    "updateDate": "24/08/2006",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/planet"
}, {
    "id": "dwarfPlanet",
    "knownCount": 5,
    "updateDate": "24/08/2006",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/dwarfPlanet"
}, {
    "id": "asteroid",
    "knownCount": 1027022,
    "updateDate": "11/11/2020",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/asteroid"
}, {
    "id": "comet",
    "knownCount": 3690,
    "updateDate": "11/11/2020",
    "rel": "https://api.le-systeme-solaire.net/rest/knowncount/comet"
}]}

const res1 = myObj.knowncount.find(el => el.id === 'planet')?.knownCount || 'Planet not found';
console.log('Know planet count:', res1);
const res2 = myObj.knowncount.find(el => el.id === 'planetX')?.knownCount || 'Planet not found';
console.log('Unknown planet count:', res2);

edited Jan 26, 2021 at 21:35

answered Jan 26, 2021 at 21:22

Israel Bessa

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7 Comments

Yevhen Horbunkov Over a year ago

This code will throw Referrence Error if id value you search for is never found.

Israel Bessa Over a year ago

What you have to show if the planet isnt found?

Yevhen Horbunkov Over a year ago

Personally, I don't need anything. I just pointed out that solution failing with error when desired result is not found (which may be pretty common thing) is not that much robust.

Israel Bessa Over a year ago

I updated my answer, try it with a unknown planet please

Yevhen Horbunkov Over a year ago

That would've been much easier to try if you would make it executable snippet.

|

MoPaMo · Accepted Answer · 2021-01-27 06:05:44Z

0

You could just loop through the object and test fo the id:

function getId(myId){
let a =myObj.knowncount
for (el in a){
   if(el.id==myId)
return el
}
}

edited Jan 27, 2021 at 6:05

answered Jan 26, 2021 at 21:18

MoPaMo

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3 Comments

MoPaMo Over a year ago

Why do you think so?

Yevhen Horbunkov Over a year ago

Do you realize that I (just like everyone else) can see you fixed your mistake after my comment?

Yevhen Horbunkov Over a year ago

And back to the 'why'-question, you might find the following quick test I've set up for you to actually prove your solution still won't work. Feel free to use it for getting your code valid.

Rohit Nishad · Accepted Answer · 2021-01-27 16:54:17Z

0

Use this getKnownCount function to get the known count.

function getKnownCount(Id) {
    let knownCountArray = myObj.knowncount;
    for (let i = 0; i < knownCountArray.length; i++) {
      if ((knownCountArray[i].id == Id)) {
        return knownCountArray[i].knownCount;
      }
    }
    return "Not found";
  }

As,

getKnownCount("planet")

or you can just simply search "planet" via the find method.

myObj.knowncount.find(el => el.id == 'planet')?.knownCount || 'Not found';

edited Jan 27, 2021 at 16:54

answered Jan 26, 2021 at 21:45

Rohit Nishad

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9 Comments

Yevhen Horbunkov Over a year ago

Your second snippet will return Not found for {id: 'planet', knownCount: 0}

Rohit Nishad Over a year ago

@YevgenGorbunkov I test it, it works fine for me can you describe more clearly what is not working for you.

Yevhen Horbunkov Over a year ago

'> it works', no, it doesn't, because it may never go further the first item, if you would have actually tested that you would figure that out

Rohit Nishad Over a year ago

@YevgenGorbunkov yeah, there is some issue I fixed it, now it work.

Rohit Nishad Over a year ago

I think you forget to accept this answer if you don't get the answer let me know.

|

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