Return just the keys of an array in AngularJS

Question

I have a solution of my question, but I don't know whether it exists a better solution.

Following I had implemented:

View:

<md-list>
   <md-list-item>
      <span ng-repeat="item in ::items track by $index" flex="auto">
          {{::item}}
      </span>
      <md-divider></md-divider>
   </md-list-item>
</md-list>

Controller:

CrudSvc.GetAll().$promise.then(
  function (res) {
     $scope.items = GetKeyForTitle(res);
  },
  function (err) {
     //err code...
  }
);

function GetKeyForTitle(data) {
   var arrItems = [];
   var resData = data[0];

   angular.forEach(resData, function (val, key) {
       arrItems.push(key);
   });

   return arrItems;
}

JSON data is simple defined:

[
  {
    "NAME": "John Doe",
    "AGE": 25,
    "CITY": "New York",
    "COUNTRY": "USA"
  },...
]

For my solution I used data[0] to give me only the first data otherwise I get always the same keys and I need the keys just one time.

@Rajesh Thanks for your comment, but in the thread there is no example to extract only the keys from the first data because I have 10 objects in the array that means in your case I would get ten times the same keys. — yuro
– yuro, Commented Nov 17, 2016 at 8:58
If I understand right, objective of question is to get keys of first object in an array of objects. Now you have already figured out the part of fetching first object. So all you need is a way to get keys, that mentioned post highlights — Rajesh Dixit
– Rajesh Dixit, Commented Nov 17, 2016 at 9:00
@Rajesh My question is, whether a better solution exists instead of using data[0]. How you can see I had already defined a forEach to loop through my array. — yuro
– yuro, Commented Nov 17, 2016 at 9:05
Have you tried Array.prototype.keys()? developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — ryanpcmcquen
– ryanpcmcquen, Commented Nov 17, 2016 at 9:18

ryanpcmcquen · Accepted Answer · 2016-11-17 09:25:31Z

3

Use Object.keys():

var data = [{
  "NAME": "John Doe",
  "AGE": 25,
  "CITY": "New York",
  "COUNTRY": "USA"
}, {
  "NAME": "John Doe",
  "AGE": 25,
  "CITY": "New York",
  "COUNTRY": "USA"
}, {
  "NAME": "John Doe",
  "AGE": 25,
  "CITY": "New York",
  "COUNTRY": "USA"
}, {
  "NAME": "John Doe",
  "AGE": 25,
  "CITY": "New York",
  "COUNTRY": "USA"
}, {
  "NAME": "John Doe",
  "AGE": 25,
  "CITY": "New York",
  "COUNTRY": "USA"
}]
var arrItems = Object.keys(data[0]);
console.log(arrItems);

https://repl.it/E0lI

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys

answered Nov 17, 2016 at 9:25

ryanpcmcquen

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5 Comments

Rajesh Dixit Over a year ago

This has been answered in post I have shared. You should not answer questions that are very basic. Instead find a similar post and mark it as duplicate

ryanpcmcquen Over a year ago

@Rajesh the accepted answer on your link uses for...in, which is no longer the preferred way of accessing Object keys.

Rajesh Dixit Over a year ago

even that is covered in that post. I guess that has highest votes.

ryanpcmcquen Over a year ago

@Rajesh, sure but it may be difficult for a beginner to know the difference.

Rajesh Dixit Over a year ago

mate i don't want a debate but it's always better to mark post duplicate. That way user will get exposure to different approach and get to know lots of caveat through comments. There is nothing wrong but please use this privilege

Ankit Tanna · Accepted Answer · 2016-11-17 09:56:52Z

0

You can use

var allKeys = [];
for(var key in myObject) allKeys.push(k);

console.log("Keys " + allKeys.length + " keys: " + allKeys);

Or if you are using Lodash/underscore they it makes your life even easier.

answered Nov 17, 2016 at 9:56

Ankit Tanna

1,8318 gold badges34 silver badges63 bronze badges

1 Comment

Ankit Tanna Over a year ago

I'll suggest you to use @ryanpcmcquen 's answer too but it looks shady when we do data[0] maybe use an object model instead

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