JavaScript: How to Fetch a object from array of objects, given an id, without using for..in loop?

Question

Let us assume that we have an array

  var mRegions = [];

This array get's populated with following object

  $.ajax(settings).done(function (response) {

                        for (var i in response.items[0].devices)
                        {

                            mRegions.push(
                                    {
                                        id: response.items[0].devices[i].id,
                                        name: response.items[0].devices[i].name,
                                        description: response.items[0].devices[i].description,
                                        uid: response.items[0].devices[i].beacon.iBeacon.uid,
                                        major: response.items[0].devices[i].beacon.iBeacon.major,
                                        minor: response.items[0].devices[i].beacon.iBeacon.minor,

                                    });
                        }



     var myId = 'b1';

At some point of time, I need to get an object from this array of objects whose id matches with the given id (myID)

Is there a way to achieve this without a for...in loop?

Phil · Accepted Answer · 2016-08-30 06:38:20Z

3

Array.prototype.find(). Make sure you read the browser compatibility section.

myRegions.find(region => region.id === myId)

or the legacy version

myRegions.find(function(r){return r.id === myId})

let myRegions = [{
  id: 'a1',
  name: 'A 1'
}, {
  id: 'a2',
  name: 'A 2'
}, {
  id: 'a3',
  name: 'A 3'
}, {
  id: 'b1',
  name: 'B 1'
}, {
  id: 'b2',
  name: 'B 2'
}];

let myId = 'b1';

let pre = document.createElement('pre');
pre.textContent = JSON.stringify(myRegions.find(region => region.id === myId), null, '  ');
document.body.appendChild(pre);

edited Aug 30, 2016 at 6:38

answered Aug 30, 2016 at 6:22

Phil

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3 Comments

Phil Over a year ago

@Rajesh Arrow functions are easily translated and if OP needs a polyfill, there's one in the linked documentation ~ developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Rajesh Dixit Over a year ago

I know that polyfill link is available, but if OP is not aware about it, he/she will use it directly and expect it to work in all browsers and when it fails on IE then they will look for polyfill. So just give a heads-up that this will happen

Phil Over a year ago

@Rajesh I don't think it's unreasonable to expect people to read the documentation, especially if they encounter an error

Amygdaloideum · Accepted Answer · 2016-08-30 06:27:54Z

If it is an option, you can use an object istead of an array, and set the keys as ids.

var mRegions = {};

$.ajax(settings).done(function (response) {
    for (var i in response.items[0].devices) {
        mRegions[response.items[0].devices[i].id] = {
          id: response.items[0].devices[i].id,
          name: response.items[0].devices[i].name,
          description: response.items[0].devices[i].description,
          uid: response.items[0].devices[i].beacon.iBeacon.uid,
          major: response.items[0].devices[i].beacon.iBeacon.major,
          minor: response.items[0].devices[i].beacon.iBeacon.minor,
        };
      }
    });

Then access the values with the following notation:

var region = mRegions.theId

Or:

var myId = 123;
var region = mRegions[myId];

Andurit · Accepted Answer · 2016-08-30 06:39:08Z

1

let array = [
   {id: 1, name: 'Name1'}, 
   {id: 3, name: 'Name3'}, 
   {id: 5, name: 'Name5'}, 
   {id: 7, name: 'Name7'}
];

let result = array.filter(function( obj ) {
  return obj.id === 5;
});

Also consider .find() function from @Phil answer.

.filter definition:

The filter() method creates a new array with all elements that pass the test implemented by the provided function.

.find definition:

The find() method returns a value in the array, if an element in the array satisfies the provided testing function. Otherwise undefined is returned.

edited Aug 30, 2016 at 6:39

answered Aug 30, 2016 at 6:21

Andurit

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2 Comments

Rohit Over a year ago

A minor update: let result = array.filter(function( obj ) { return obj.id === 5; });

Andurit Over a year ago

@RDX didn't noticed I have just 2x =, thanks for it. Edited

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