javascript : nullish-coalescing

nullish-coalescing.js

//nullidh coalescing operator ?? is only case null, undefined check.'
//do not confusing to Logical OR operator || is only case false(0, undefined, null, "",'',``) or true check.

//bad code
function printMessage(test){
  let message = text;
  if(text == null || text == undefined) {
    message = 'Nothing to display';
  }
  console.log(message);
}

//good code
function printMessage(text){
  const message = text ?? 'Nothing to display';
  console.log(message)
}

//default parameter is only for undefined
function printMessage(text = 'Nothing to display') {
  console.log(text);
}

//Logical OR operator
function printMessage(text){
  const message = text || 'Nothing to display';
  console.log(message)
}

printMessage('hello');
printMessage(undefined);
printMessage(null);
printMessage(0);
printMessage("");


//another case using nullidh coalescing
const result = getInitialState() ?? fetchFromServer();
console.log(result);

function getIni9tialState() {
  return null;
}
function fetchFromServer() {
  return 'Hiya from german';
}