CODEWITHSUNDEEP
javascriptarraysjsonangularjsng-options
Raj Adroit
Raj Adroit

Reputation: 3878

AngularJS dropdown not showing selected value

Am facing problem in displaying selected value in angular dropdown. it works when i give like this

$scope.selectedItem = $scope.items[1];

not working, if i give directly that value 

$scope.selectedItem = { name: 'two', age: 27 };

HTML:

<html ng-app="app">
  <body>
    <div ng-controller="Test">
      <select ng-model="selectedItem" ng-options="item.name for item in items">
      </select>
    </div>
  </body>
</html>

JS:

var app = angular.module('app',[]);
app.controller('Test',function($scope){
   $scope.items = [{name: 'one', age: 30 },{ name: 'two', age: 27 },{ name: 'three', age: 50 }];
  $scope.selectedItem = $scope.items[1];
});

CODEPEN: http://codepen.io/anon/pen/zxXpmR

SOLUTION:

Thank you samir-das. I fixed as per your suggestion. 

var choosen_value = { name: 'two', age: 27 };
angular.forEach($scope.items, function(item){
  if(angular.equals(choosen_value, item)){
    $scope.selectedItem = item;
  }
});

Upvotes: 10

Views: 17753

Answers (4)

Samir Das
Samir Das

Reputation: 1908

Well, because

$scope.items[1] and { name: 'two', age: 27 } is totally different thing.

{ name: 'two', age: 27 } is a totally different object whereas $scope.items[1] is part of the object $scope.items

When you put something in the template using {{}}, angular add it in its watcher list.

SO when angular put it in the watch list, it was an object (i.e. { name: 'two', age: 27 } ) that is different than $scope.items.

selectedItem is attached with the object that you set in the controller. In summary while dirty checking, angular will checks selectedItem against { name: 'two', age: 27 } NOT against $scope.items

Hope you understand what I mean

Upvotes: 6

noj
noj

Reputation: 6759

As explained in the other answers, while the two objects may have the same properties and values, they are two different objects so angular doesn't consider them to be equal.

You can however use the track by expression in ng-options to specify a property which will decide equality:

ng-options="item.name for item in items track by item.name"

http://codepen.io/anon/pen/WbWMrp

Upvotes: 7

Himanshu Mittal
Himanshu Mittal

Reputation: 804

In angular, Arrays and objects are passed by reference while strings, numbers and booleans are passed by value. So, angular interprets $scope.items[1] and { name: 'two', age: 27 } as two different objects. That's why your binding fails when you do $scope.selectedItem = { name: 'two', age: 27 }; directly and find it in '$scope.items'.

Upvotes: 1

Tade&#225;š Pet&#225;k
Tade&#225;š Pet&#225;k

Reputation: 567

This is not an Angular feature/issue, it is a consequence of how object equality works in Javascript. This article does a fairly good job in explaining what is going on in a pretty concise way and gives some examples. Check out the source of lodash's isEqual method (it will take you to the definition of baseIsEqualDeep eventually) to see how what you are trying to achieve can be done in pure JS.

In any case, I do not think there is an easy way to achieve this in Angular, you would have to re-write the way ng-options works and you probably do not want to go there...

Upvotes: 1

Related Questions