$('.button').click(function() {
const $this = $(this);
const $content = $this.closest('.item').find('.block');
if ($this.hasClass('closed')) {
$this.removeClass('closed').html('Скрыть ↑');
$content.slideDown();
} else {
$this.addClass('closed').html('Показать ↓');
$content.slideUp();
}
}).click();