JSFiddle - React, Tailwind, and code Playground

HTML

<div class="num" data-str="KzM4MCAoOTUpIDYzMi00Mi01MQ==">
  <a class="num_hide">(XX) XXX-XX-XX</a> 
  <span class="sh_nmr">показать</span>
</div>

CSS

.sh_nmr {
  cursor: pointer;
}

JavaScript

$('.sh_nmr').click(function(){
	if( ! $(this).hasClass('on')){
    $numb = window.atob($('.num').attr('data-str'))
		$('.num_hide').text($numb)
                  .attr('href' , 'tel:' +  $numb.replace(/[^0-9\+]/ig,""));
    $(this).addClass('on');
    $(this).hide();
	}else{
		$('.num').attr('data-str', window.btoa($('.num_hide').text()));
		$('.num_hide').text('(XX) XXX-XX-XX')
                  .removeAttr('href');
    $(this).removeClass('on');
  }
});