var uri = 'https://mozilla.org/?x=шеллы';
var encoded = encodeURI(uri);
console.log(encoded);
// expected output: "https://mozilla.org/?x=%D1%88%D0%B5%D0%BB%D0%BB%D1%8B"

try {
  console.log(decodeURI(encoded));
  // expected output: "https://mozilla.org/?x=шеллы""
} catch(e) { // catches a malformed URI
  console.error(e);
}