JSFiddle - React, Tailwind, and code Playground

HTML

<span ng-init="foo=[1,2,3,4]" ng-app="app">
    <span ng-repeat="f in foo">{{f}}<span ng-if="!$last">,</span></span>
    <p>{{foo|arrayToList}}</p>
</span>

JavaScript

angular.module('app', []).filter('arrayToList', function(){
    return function(arr) {
        return arr.join(',');
    }
});