Angularjs groupBy + orderBy

Question

I am using groupBy from angular-filter to group an array of objects by their date property.

<div ng-repeat="(day, dayEvents) in events | groupBy: 'date' )">
 <h3>{{ day | date: mediumDate }}</h3>
</div>

Which produces the following:

Feb 9, 2015 
Feb 10, 2015 
Feb 11, 2015 
Feb 12, 2015 

How can I reverse the order to start from the most recent date? When I print to the console the array is printed with the order I want:

  Object {
     1423699200000: Array[1],
     1423612800000: Array[7],
     1423526400000: Array[11],
     1423440000000: Array[1]
 }

I also wrote a custom filter to reverse the order after the groupBy:

.filter("reverseOrder", function() {
        function sortNumber(a,b) {
            return  parseInt(b) - parseInt(a);
        }
        return function(collection) {
            var keys = Object.keys(collection).sort(sortNumber);
            var reveredCollection= {};
            var length=collection.length;
            angular.forEach(keys, function(key) {
                reveredCollection[key] = collection[key];
            });
           return reveredCollection;
        }
    })

Which I have applied like this:

<div ng-repeat="(day, dayEvents) in events | groupBy: 'date' | reverseOrder )">
     <h3>{{ day | date: mediumDate }}</h3>
</div>

Answer 1

Recently had the same issue. groupBy creates an object, but the orderBy needs an array, so there's a little bit of funkiness involved. I ended up getting the answer straight from their issues page where one of the authors does an excellent job of explaining it complete with code samples that was basically copy/paste for me.

https://github.com/a8m/angular-filter/issues/57#issuecomment-65041792

Answer 2

We can achieve this by ordering the data in controller & converting groupBy output to Array.

In controller, order the records before sending it to view :

$scope.events = $filter('orderBy')(events, '-date');

Now the template, receives data in sorted order. After grouping, we need to transform it to Array :

<div ng-repeat="(day, dayEvents) in events | groupBy: 'date' | toArray:true )">
     <h3>{{ day | dayEvents[0].date: mediumDate }}</h3>
</div>