JSFiddle - React, Tailwind, and code Playground

JavaScript

function myfun()
{
  var a = "'\\u0c39";
  a = a.replace(/\\u([a-f0-9]{4})/i, function (n, hex) {
      return String.fromCharCode(parseInt(hex, 16));
  });

  alert(a);

}
function myfun1()
{
  var a = "'\\u0c39";
  alert(a.replace("\\\\","\\").toString());

}

myfun();
myfun1();