How to make changing numbers and make them both work?

Question

JavaScript

There is not enough space in the header to insert 2 numbers, so I would like to make it so that the number is displayed, but only mobile operators change (the numbers are identical, only the operators differ), how can this be implemented, and so that both numbers would work correctly?

Answer 1

<a id="phone" href=""><a/>

document.addEventListener('DOMContentLoaded', function() {
  var link = document.getElementById('phone');
  var a = '[phone]';
  var b = '[phone]';
  
  link.innerText = b;
  link.setAttribute('href', 'tel:' + b);
  
  setInterval(function() {
    link.innerText = link.innerText === b ? a : b;
    link.setAttribute('href', 'tel:' + link.innerText);
  }, 1000);
});