JavaScript-da Promise-larda istisnolarni alohida tutish

then-da faqat istisno holatini qayta ishlovchi funktsiyani ko'rsatish mumkin, birinchi parametr o'rniga null berish orqali:

javascriptpromise.then(
  null,
  function(error) {
    console.log(error);
  }
);

Bunday holatda catch metodi orqali qisqartirilgan sintaksisdan foydalanish qulay:

javascriptpromise.catch(
  function(error) {
    console.log(error);
  }
);

javascriptlet promise = new Promise(function(resolve, reject) {
  setTimeout(function() {
    let isError = false;
    
    if (!isError) {
      resolve('success');
    } else {
      reject(new Error('error'));
    }
  }, 3000);
});

promise.then(
  res => console.log(res),
  err => console.log(err.message),
);