Finding value of javascript object in an array

Question

Hi really new to javascript and am hoping to get some help with a problem im facing.

So I basically have an array that stores objects. Each object contains an id and a variable i which is a number. My question is this: how can I extract the value of i from the object array with the id value? The id that I am using would already have been stored in the array with an i value.

var i = 1;
var id;
var b = {}; 
var y = [];

if(condition) {

  b = {"123":i};

  y.push(b);

}

if(condition) {
  id = 123;
  //Find corresponding i value for id "123" from object array y
  i = ?;
}

Possible duplicate of [Find object by id in an array of JavaScript objects](https://stackoverflow.com/questions/7364150/find-object-by-id-in-an-array-of-javascript-objects) — Jared Smith, Jun 28 '17 at 16:41
The suggested solutions are for jQuery. Will they work for javascript too? @JaredSmith — user3702643, Jun 28 '17 at 16:45
[Array#find](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/find) — Xotic750, Jun 28 '17 at 16:46
[Array#find](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/find) is not jQuery. I actually don't see any jQuery solutions suggested (yet). And remember, jQuery *is* JavaScript. — Mark Rabey, Jun 28 '17 at 17:17

Xotic750 · Answer 1 · 2017-06-28T18:06:42.520

1

An example with Array#find

var hasOwn = Function.prototype.call.bind(Object.prototype.hasOwnProperty);
var i = 1;
var id;
var b = {};
var y = [];

var condition = true;
if (condition) {
  b = {
    "123": i
  };

  y.push(b);
}

if (condition) {
  id = 123;
  // Find corresponding i value for id "123" from object array y
  // i = ? ;
  var found = y.find(function(o) {
    return hasOwn(o, id);
  });
  var f = found ? found[id] : found;
  console.log(f);
}

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edited Jun 28 '17 at 18:06

answered Jun 28 '17 at 17:00

Xotic750

22,914
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While this answer does find the value of "i", the items array doesn't match the example that was given by the OP. – abbotto Jun 28 '17 at 17:36
No, because this was posted before the Q was edited. :) – Xotic750 Jun 28 '17 at 17:42
There can be issues with calling "hasOwnProperty" in some browsers. Example: https://stackoverflow.com/questions/8157700/object-has-no-hasownproperty-method-i-e-its-undefined-ie8 – abbotto Jun 28 '17 at 17:54
Like I care about IE8. :D – Xotic750 Jun 28 '17 at 17:59

score 0 · Answer 2 · answered Jun 28 '17 at 16:44

0

Just use ObjectName[Key] this is enoughto get you the value Like b[123]

answered Jun 28 '17 at 16:44

Rahul Singh

19,030
11
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Ved · Answer 3 · 2017-06-28T17:02:32.397

0

Many ways to do this. Here is one of them.

var arr = [{id:1},{id:123}];

var obj = arr.filter(function(val){
   if(val.id===123)
  return val

})

console.log(obj,'obj')

edited Jun 28 '17 at 17:02

answered Jun 28 '17 at 16:45

Ved

11,837
5
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the output i get for this is [] 'obj'. Any idea why? – user3702643 Jun 28 '17 at 16:54
@user3702643 have you run the snippet. – Ved Jun 28 '17 at 16:57
I ran it on my local environment. Cant seem to get the same result. – user3702643 Jun 28 '17 at 16:59
[Array#filter](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter) will always give you an array, and it may contain 0 or 1 or more elements. It's probably not the best choice in this use case. – Xotic750 Jun 28 '17 at 17:08
@Xotic750 correct. but we dont know if the ID is duplicate. – Ved Jun 28 '17 at 17:14
Find all matching wasn't hinted at, hence I say probably. :) – Xotic750 Jun 28 '17 at 17:16
@Xotic750c actually he need just `i` value. So it will have only one value. – Ved Jun 28 '17 at 17:23

abbotto · Answer 4 · 2017-06-28T18:34:44.873

0

You can loop through the array and get the object property value as follows:

var arr = [
    {"123": "valueA"},
    {"456": "valueB"}
];

const id = "123";
let value;

arr.some(obj => {
    if (obj[id] || obj[id] === 0) value = obj[id];
});

console.log(value);

Documentation for "Array.some" method

edited Jun 28 '17 at 18:34

answered Jun 28 '17 at 16:55

abbotto

4,259
2
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1

It would be better to use [Array#some](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/some) than [Array#forEach](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach) – Xotic750 Jun 28 '17 at 16:58
What if the value for `i` was `0`? – Xotic750 Jun 28 '17 at 17:53
The correct value for "0" should be returned - now that I've updated the answer. :) – abbotto Jun 28 '17 at 18:35
The keywords `const` and `let`, and `Arrow functions` can cause an issue in some browsers. ;) – Xotic750 Jun 28 '17 at 18:41

score 0 · Answer 5 · answered Jun 28 '17 at 17:29

const stuff = [
  {
    name: 'Leonardo',
    id: 100
  },
  {
    name: 'Donatello',
    id: 101
  },
  {
    name: 'Raphael',
    id: 102
  },
  {
    name: 'Michaelangelo',
    id: 103
  },
];

First, use the Array.prototype.find() method on the array to find the object within it that has the desired ID and store it in the entry variable. Then, log the value corresponding to the name key within that object.

const desired = 102;
const entry = stuff.find(item => item.id === desired);

console.log(entry.name);

Finding value of javascript object in an array

5 Answers5