public/javascript/libs/select2.js
function () {
            var placeholder = this.getPlaceholder();

            if (this.isPlaceholderOptionSelected() && placeholder !== undefined) {

                // check for a placeholder option if attached to a select
                if (this.select && this.getPlaceholderOption() === undefined) return;

                this.selection.find(".select2-chosen").html(this.opts.escapeMarkup(placeholder));

                this.selection.addClass("select2-default");

                this.container.removeClass("select2-allowclear");
            }
        }
function () {
            var placeholder = this.getPlaceholder();

            if (this.isPlaceholderOptionSelected() && placeholder !== undefined) {

                // check for a placeholder option if attached to a select
                if (this.select && this.getPlaceholderOption() === undefined) return;

                this.selection.find(".select2-chosen").html(this.opts.escapeMarkup(placeholder));

                this.selection.addClass("select2-default");

                this.container.removeClass("select2-allowclear");
            }
        }
single