For displaying symfony collections

symfony_collection.js

(function () {
                function SymfonyCollection(listId, addBtnId, count) {
                    this.list = $('#' + listId);
                    this.count = count;
                    this.widget = this.list.attr('data-prototype');

                    var _self = this;

                    $('#' + addBtnId).on('click', function () {
                        _self.add();
                    });

                    this.list.find('.form-group').each(function () {
                        _self.addRemoveButton($(this));
                    });
                }

                SymfonyCollection.prototype.list = undefined;
                SymfonyCollection.prototype.count = undefined;
                SymfonyCollection.prototype.widget = undefined;

                SymfonyCollection.prototype.add = function () {
                    this.list.append(this.getWidget());
                };

                SymfonyCollection.prototype.getWidget = function () {
                    var widget = $(this.widget.replace(/__name__/g, this.count));
                    this.addRemoveButton(widget);
                    this.count++;

                    return widget;
                };

                SymfonyCollection.prototype.addRemoveButton = function ($formGroup) {
                    $formGroup.addClass('input-group');
                    var $rmBtn = $('<span class="input-group-btn"><button type="button" class="btn btn-danger"><i class="glyphicon glyphicon-remove"></i></button></span>');
                    $formGroup.append($rmBtn);

                    $rmBtn.on('click', function (e) {
                        e.preventDefault();
                        $formGroup.remove();
                    })
                };

                var length = '{{ form.ips|length }}';
                $collection = new SymfonyCollection('sandbox_form_ips', 'js-add-ip', length);

                if (length == 0) {
                    $collection.add();
                }
            })();