Unable to call Object.keys in angularjs

I’m using a UI.Bootstrap accordion and I’ve defined my heading like so:

<accordion-group ng=repeat="(cname, stations) in byClient">
    <accordion-heading>
        {{ cname }} <span class="pull-right"> {{ Object.keys(stations).length }} Stations</span>
    </accordion-heading>

When that displays the Object.keys(stations).length resolves to nothing. If I put that same length call in my controller I get back the expected count. Is there something preventing the method call from working in AngularJS?

The rest of the accordion that uses stations acts as expected, so I know that it’s being populated properly. The byClient data structure basically looks like so:

{
    "Client Name" : {
        "Station Name": [
            {...},
            {...}
        ]
    }
 }

Answer

Yes, That is because Object is a part of window/global and angular cannot evaluate that expression against the scope. When you specify Object.keys in your binding angular tries to evaluate it against the $scope and it does not find it. You could store the reference of object.keys in some utility in rootScope and use it anywhere in the app.

Something like this:-

angular.module('yourApp',[deps...]).run(function($rootScope){
  //Just add a reference to some utility methods in rootscope.
  $rootScope.Utils = {
     keys : Object.keys
  }

  //If you want utility method to be accessed in the isolated Scope 
  //then you would add the method directly to the prototype of rootScope 
  //constructor as shown below in a rough implementation.

  //$rootScope.constructor.prototype.getKeys = Object.keys;

});

and use this as:-

<span class="pull-right"> {{ Utils.keys(stations).length }} Stations</span>

Well this will be available to any child scopes except for isolated scopes. If you are planning to do it on the isolated scope (eg:- Isolated scoped directives) you would need to add the reference of Object.keys on the scope, or as you expose a method on the scope which will return the length.

Or better yet , create a format filter to return the keylength and use it everywhere.

app.filter('keylength', function(){
  return function(input){
    if(!angular.isObject(input)){
      throw Error("Usage of non-objects with keylength filter!!")
    }
    return Object.keys(input).length;
  }
});

and do:-

{{ stations | keylength }}

Demo