How to get an object out of an array without knowing its index, only 'key' name

Question

With 2 arrays (one of numbers and other of objects),
How can I get a specific object's-(size) value (in other function) without knowing its index (and it's value) in the array only its key
with the shortest and fastest way so I can use that value number ?

If the array is empty except for this specific object, the size property value will be - 0;

If my question isn't clear please comment and I'll fix it and make it betters.

let firstArray = [ 1, 2 , 10, 23, {size: 890}];
     
   funcExtract(firstArray);
    
   function funcExtract(arr){
        
    // arr ? How to find the object when knowing only its key
    }

And with array of objects

let secondArray  = [ {a:2}, {b:4 },{size: 700}, {c:5} ];
 
      funcExtract(secondArray); 

      function funcExtract(arr){
        
      }

Please remove reactjs from the post tags. It's not relevant for what you're asking. — emerson.marini
– emerson.marini, Commented Aug 12, 2021 at 10:53
Your first array has numbers and an object that has a size property. What is the "specific object" you're looking for? Can you give some examples? — AKX
– AKX, Commented Aug 12, 2021 at 10:53
{size: 890} in this case the key is "size", and the value is 890 — Elassoa
– Elassoa, Commented Aug 12, 2021 at 11:02

Sinan Yaman · Accepted Answer · 2021-08-12 10:54:15Z

2

You can use the Array#find function:

const test = [1, 2, 3, 4, {key: 5}]
const findOne = test.find(item => item.hasOwnProperty("key"))
console.log(findOne)

edited Aug 12, 2021 at 10:54

answered Aug 12, 2021 at 10:48

Sinan Yaman

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2 Comments

Elassoa Over a year ago

I meant I don't need know the key's value. important

Sinan Yaman Over a year ago

What do you mean by knowing only its key then?. Updated answer, take a look

Majid M. · Accepted Answer · 2021-08-12 11:02:07Z

1

Here's the thing which you can do it:

let key = "size"
let secondArray  = [ {a:2}, {b:4 },{size: 700}, {c:5} ];
let firstArray = [ 1, 2 , 10, 23, {size: 890}];
function funcExtract(arr,key){
   let filter = arr.filter((x)=> typeof x === "object" && x.hasOwnProperty(key))
   console.log(filter[0].size)
}
funcExtract(firstArray,key);
funcExtract(secondArray,key);

answered Aug 12, 2021 at 11:02

Majid M.

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1 Comment

Elassoa Over a year ago

Yes your way works, but I found here to better use the find method, it's a shorter way. Thanks

Red Baron · Accepted Answer · 2021-08-12 10:53:34Z

0

let secondArray  = [ {a:2}, {b:4 },{size: 700}, {c:5} ];
secondArray.find(o => o.size) // {size: 700}
a.filter(o => o.size) // good if you need to find more than 1 with same key

edited Aug 12, 2021 at 10:53

answered Aug 12, 2021 at 10:51

Red Baron

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5 Comments

spender Over a year ago

What if o.size is 0 (i.e. falsey)?

Red Baron Over a year ago

well presumably the OP can add their own safeguards, think that's out of the scope of the question

Elassoa Over a year ago

@RedBaron I updated my question, regards to size = 0

Red Baron Over a year ago

I'm not sure I understand the new question. does my answer not work? and if not, which part does not work?

Elassoa Over a year ago

@RedBaron When {size: 0} it will be > undefined. Than I will use find(o => o.hasOwnProperty("size")); Thanks

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