Promise.prototype.catch() - JavaScript

Method catch() mengembalikan Promise dan hanya setuju jika kasusnya gagal. Sama halnya dengan memenggil method Promise.prototype.then(undefined, onRejected).

Sintaks

p.catch(onRejected);

p.catch(function(reason) {
   // rejection
});

Parameter

onRejected: Function dipanggil ketika Promise ditolak. Fungsi ini memiliki satu argumen, alasan penolakan.

Deskripsi

Method catch sangat berguna untuk menangani error di gabungan promis anda.

Contoh

Penggunaan method `catch`

var p1 = new Promise(function(resolve, reject) {
  resolve('Success');
});

p1.then(function(value) {
  console.log(value); // "Success!"
  throw 'oh, no!';
}).catch(function(e) {
  console.log(e); // "oh, no!"
}).then(function(){
  console.log('after a catch the chain is restored');
}, function () {
  console.log('Not fired due to the catch');
});

// The following behaves the same as above
p1.then(function(value) {
  console.log(value); // "Success!"
  return Promise.reject('oh, no!');
}).catch(function(e) {
  console.log(e); // "oh, no!"
}).then(function(){
  console.log('after a catch the chain is restored');
}, function () {
  console.log('Not fired due to the catch');
});

Promis tidak dapat mendeteksi error pada asynchronous callback

var p1 = new Promise(function(resolve, reject) {
  throw 'Uh-oh!';
});

p1.catch(function(e) {
  console.log(e); // "Uh-oh!"
});


var p2 = new Promise(function(resolve, reject) {
  setTimeout(function() {
    throw 'Uncaught Exception!';
  }, 1000);
});

p2.catch(function(e) {
  console.log(e); // This is never called
});

Spesifikasi

Spesifikasi	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Promise.prototype.catch' in that specification.	Standard	Initial definition in an ECMA standard.
ECMAScript (ECMA-262) The definition of 'Promise.prototype.catch' in that specification.	Living Standard

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