Using comma as list separator with AngularJS

You could do it this way:

<b ng-repeat="email in friend.email">{{email}}{{$last ? '' : ', '}}</b>

..But I like Philipp's answer :-)

Also:

angular.module('App.filters', [])
    .filter('joinBy', function () {
        return function (input,delimiter) {
            return (input || []).join(delimiter || ',');
        };
    });

And in template:

{{ itemsArray | joinBy:',' }}

Just use Javascript's built-in join(separator) function for arrays:

<li ng-repeat="friend in friends">
  <b>{{friend.email.join(', ')}}</b>...
</li>