JSFiddle - React, Tailwind, and code Playground

JavaScript

function toAbsURL(s) { 
     var l = location, h, p, f, i; 
     if (/^\w+:/.test(s)) { 
       return s; 
     } 
     h = l.protocol + '//' + l.host; 
     if (s.indexOf('/') == 0) { 
       return h + s; 
     } 
     p = l.pathname.replace(/\/[^\/]*$/, ''); 
     f = s.match(/\.\.\//g); 
     if (f) { 
       s = s.substring(f.length * 3); 
       for (i = f.length; i--;) { 
         p = p.substring(0, p.lastIndexOf('/')); 
       } 
     } 
     return h + p + '/' + s; 
   }

alert(window.location.href);
alert(toAbsURL('../../'));