JSFiddle - React, Tailwind, and code Playground

HTML

<span id="old-1">Some text</span>
<span id="new-2">new</span>
<span id="old-3">Some text</span>
<span id="new-4">new</span>

JavaScript

$('span').each(function()
        {
            var idnum = $(this).attr('id').match(/[\d]/);
            $('#new-' + idnum).text("span id "+idnum+" changed.");
            $('#old-' + idnum).text("span id "+idnum+" changed.");
            
        }
        
    );