JSFiddle - React, Tailwind, and code Playground

JavaScript

function rot13(str) { // LBH QVQ VG!
  var strAry = str.split('');

  var transformed = strAry.map(function(val){

    if(val === " ") return " ";
    else{
      var code = val.charCodeAt(0);
      return  String.fromCharCode(code-13);
    }
  });
  transformed = transformed.join('');
 console.log(transformed);
  return transformed;
}

// Change the inputs below to test
rot13("SERR PBQR PNZC");