Promise

Bu çeviri eksik. Bu makaleyi İngilizceden tercüme etmemize yardım edin

Promise nesnesi eşzamansız olan ve ertelenen işlemlerde kullanılır. Bir Promise nesnesi henüz işlemin tamamlamadığını ama sonradan tamamlanabileceğini gösterir.

Sözdizimi

new Promise(function(resolve, reject) { ... });

Parametreler

executor
resolve ve reject içeren iki parametreli bir fonksiyon nesnesidir. İlk parametre promise nesnesi tamamlandığında, ikinci parametre ise reddettiğinde çağrılır. Bu fonksiyonları işlemimiz bittiğinde (başarılı yada başarısız) çağırırız.

Açıklama

Oluşturulan bir promise başka bir promise için proxy görevi görür.
Başarılı yada başarısız bir şekilde sonuç üreten asenkron işlemlerin ilişkilendirilmesine olanak tanır.Bu asenkron methodların senkron methodlar gibi sonuç döndürmesi'ni sağlar.Asenkron method hemen sonuçlanmaz.Bunun yerine işlemin tamamlandığı noktayı temsil eden bir promise döndürür.

Bir Promise şu durumları içerir:

  • pending: ne işlem görmüş ne de red edilmiş başlangıç durumu.
  • fulfilled: operasyon ' un başarılı bir şekilde tamamlandığı durum.
  • rejected: operasyon ' un başarısızlıkla tamamlandığı durum.

Bekleyen bir Promise, bir sonuç döndürerek tamamlanabilir veya bir nedenle reddedilebilir(hata).Bunlardan herhanbiri gerçekleştiğinde (resolve/reject) sıraya konulmuş ilişkili methodlar sıra ile çağrılır.(Promise tamamlandığında yada red edildiğinde sırada bağlanmış bir method var ise o method çalıştırılır.Böylece asenkron işlemler arasında bir rekabet/mücadele olmaz.Sırası gelen çalışır.)

As the Promise.prototype.then() and Promise.prototype.catch() methods return promises, bunlar zincirlenebilirler—an operation called composition.

Note: A promise is said to be settled if it is either fulfilled or rejected, but not pending. You will also hear the term resolved used with promises — this means that the promise is settled, or it is locked into a promise chain. Domenic Denicola's States and fates contains more details about promise terminology.

Özellikler

Promise.length
Değeri 1 olan Length özelliği (constructor argümanları sayısı).
Promise.prototype
Represents the prototype for the Promise constructor.

Metodlar

Promise.all(iterable)
Returns a promise that either resolves when all of the promises in the iterable argument have resolved or rejects as soon as one of the promises in the iterable argument rejects. If the returned promise resolves, it is resolved with an array of the values from the resolved promises in the iterable. If the returned promise rejects, it is rejected with the reason from the promise in the iterable that rejected. This method can be useful for aggregating results of multiple promises together.
Promise.race(iterable)
Returns a promise that resolves or rejects as soon as one of the promises in the iterable resolves or rejects, with the value or reason from that promise.
Promise.reject(reason)
Belirtilen bir nedenden dolayı reddedilen Promise nesnesini döndürür.
Promise.resolve(value)
Returns a Promise object that is resolved with the given value. If the value is a thenable (i.e. has a then method), the returned promise will "follow" that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value. Generally, if you want to know if a value is a promise or not - Promise.resolve(value) it instead and work with the return value as a promise.

Promise prototype

Özellikler

Metodlar

Örnekler

Promise Oluşturma

Bu küçük örnek Promise mekanizmasını gösterir. <button> her tıklandığında testPromise() metodu çağrılır . It creates a promise that will resolve, using window.setTimeout(), to the string "result" every 1-3 seconds, at random. The Promise() constructor is used to create the promise.

The fulfillment of the promise is simply logged, via a fulfill callback set using p1.then(). A few logs shows how the synchronous part of the method is decoupled of the asynchronous completion of the promise.

'use strict';
var promiseCount = 0;

function testPromise() {
    var thisPromiseCount = ++promiseCount;

    var log = document.getElementById('log');
    log.insertAdjacentHTML('beforeend', thisPromiseCount +
        ') Started (<small>Sync code started</small>)<br/>');

    // We make a new promise: we promise the string 'result' (after waiting 3s)
    var p1 = new Promise(
        // The resolver function is called with the ability to resolve or
        // reject the promise
        function(resolve, reject) {
            log.insertAdjacentHTML('beforeend', thisPromiseCount +
                ') Promise started (<small>Async code started</small>)<br/>');
            // This is only an example to create asynchronism
            window.setTimeout(
                function() {
                    // We fulfill the promise !
                    resolve(thisPromiseCount);
                }, Math.random() * 2000 + 1000);
        });

    // We define what to do when the promise is resolved/fulfilled with the then() call,
    // and the catch() method defines what to do if the promise is rejected.
    p1.then(
        // Log the fulfillment value
        function(val) {
            log.insertAdjacentHTML('beforeend', val +
                ') Promise fulfilled (<small>Async code terminated</small>)<br/>');
        })
    .catch(
        // Log the rejection reason
        function(reason) {
            console.log('Handle rejected promise ('+reason+') here.');
        });

    log.insertAdjacentHTML('beforeend', thisPromiseCount +
        ') Promise made (<small>Sync code terminated</small>)<br/>');
}

Bu örnek buton'a tıkladığınızda çalışır. Promise destekleyen bir tarayıcıya ihtiyacınız var. Buton'a birden fazla tıklamanız durumunda farklı promise nesnelerinin kısa sürede tamamlandığını göreceksiniz.

new XMLHttpRequest() Kullanım Örneği

Promise Oluşturma

Bu örnekte XMLHttpRequest nesnesinin başarılı yada başarısız durumunu Promise kullanarak nasıl raporlanabildiğini göstermektedir.

'use strict';

// A-> $http function is implemented in order to follow the standard Adapter pattern
function $http(url){
 
  // A small example of object
  var core = {

    // Method that performs the ajax request
    ajax : function (method, url, args) {

      // Creating a promise
      var promise = new Promise( function (resolve, reject) {

        // Instantiates the XMLHttpRequest
        var client = new XMLHttpRequest();
        var uri = url;

        if (args && (method === 'POST' || method === 'PUT')) {
          uri += '?';
          var argcount = 0;
          for (var key in args) {
            if (args.hasOwnProperty(key)) {
              if (argcount++) {
                uri += '&';
              }
              uri += encodeURIComponent(key) + '=' + encodeURIComponent(args[key]);
            }
          }
        }

        client.open(method, uri);
        client.send();

        client.onload = function () {
          if (this.status >= 200 && this.status < 300) {
            // Performs the function "resolve" when this.status is equal to 2xx
            resolve(this.response);
          } else {
            // Performs the function "reject" when this.status is different than 2xx
            reject(this.statusText);
          }
        };
        client.onerror = function () {
          reject(this.statusText);
        };
      });

      // Return the promise
      return promise;
    }
  };

  // Adapter pattern
  return {
    'get' : function(args) {
      return core.ajax('GET', url, args);
    },
    'post' : function(args) {
      return core.ajax('POST', url, args);
    },
    'put' : function(args) {
      return core.ajax('PUT', url, args);
    },
    'delete' : function(args) {
      return core.ajax('DELETE', url, args);
    }
  };
};
// End A

// B-> Here you define its functions and its payload
var mdnAPI = 'https://developer.mozilla.org/en-US/search.json';
var payload = {
  'topic' : 'js',
  'q'     : 'Promise'
};

var callback = {
  success : function(data){
     console.log(1, 'success', JSON.parse(data));
  },
  error : function(data){
     console.log(2, 'error', JSON.parse(data));
  }
};
// End B

// Executes the method call 
$http(mdnAPI) 
  .get(payload) 
  .then(callback.success) 
  .catch(callback.error);

// Executes the method call but an alternative way (1) to handle Promise Reject case 
$http(mdnAPI) 
  .get(payload) 
  .then(callback.success, callback.error);

// Executes the method call but an alternative way (2) to handle Promise Reject case 
$http(mdnAPI) 
  .get(payload) 
  .then(callback.success)
  .then(undefined, callback.error);

XHR ile görsel yükleme

Another simple example using Promise and XMLHttpRequest to load an image is available at the MDN GitHub promise-test repository. You can also see it in action. Each step is commented and allows you to follow the Promise and XHR architecture closely.

Specifications

Specification Durum Yorum
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Promise' in that specification.
Standard Initial definition in an ECMA standard.
ECMAScript (ECMA-262)
The definition of 'Promise' in that specification.
Living Standard

Tarayıcı uyumluluğu

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
PromiseChrome Full support 32Edge Full support 12Firefox Full support 29IE No support NoOpera Full support 19Safari Full support 8WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29Opera Android Full support 19Safari iOS Full support 8Samsung Internet Android Full support 2.0nodejs Full support 0.12
Promise() constructorChrome Full support 32Edge Full support 12Firefox Full support 29
Notes
Full support 29
Notes
Notes Constructor requires a new operator since version 37.
IE No support NoOpera Full support 19Safari Full support 8
Notes
Full support 8
Notes
Notes Constructor requires a new operator since version 10.
WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29
Notes
Full support 29
Notes
Notes Constructor requires a new operator since version 37.
Opera Android Full support 19Safari iOS Full support 8
Notes
Full support 8
Notes
Notes Constructor requires a new operator since version 10.
Samsung Internet Android Full support 2.0nodejs Full support 0.12
Notes
Full support 0.12
Notes
Notes Constructor requires a new operator since version 4.
all()Chrome Full support 32Edge Full support 12Firefox Full support 29IE No support NoOpera Full support 19Safari Full support 8WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29Opera Android Full support 19Safari iOS Full support 8Samsung Internet Android Full support 2.0nodejs Full support 0.12
allSettled()Chrome Full support 76Edge Full support 79Firefox Full support 71IE No support NoOpera Full support 63Safari Full support 13WebView Android Full support 76Chrome Android Full support 76Firefox Android No support NoOpera Android Full support 54Safari iOS Full support 13Samsung Internet Android No support Nonodejs Full support 12.9.0
anyChrome Full support 85Edge No support NoFirefox Full support 79IE No support NoOpera No support NoSafari Full support 14WebView Android Full support 85Chrome Android Full support 85Firefox Android Full support 79Opera Android No support NoSafari iOS Full support 14Samsung Internet Android No support Nonodejs No support No
catch()Chrome Full support 32Edge Full support 12Firefox Full support 29IE No support NoOpera Full support 19Safari Full support 8WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29Opera Android Full support 19Safari iOS Full support 8Samsung Internet Android Full support 2.0nodejs Full support 0.12
finally()Chrome Full support 63Edge Full support 18Firefox Full support 58IE No support NoOpera Full support 50Safari Full support 11.1WebView Android Full support 63Chrome Android Full support 63Firefox Android Full support 58Opera Android Full support 46Safari iOS Full support 11.3Samsung Internet Android Full support 8.0nodejs Full support 10.0.0
race()Chrome Full support 32Edge Full support 12Firefox Full support 29IE No support NoOpera Full support 19Safari Full support 8WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29Opera Android Full support 19Safari iOS Full support 8Samsung Internet Android Full support 2.0nodejs Full support 0.12
reject()Chrome Full support 32Edge Full support 12Firefox Full support 29IE No support NoOpera Full support 19Safari Full support 8WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29Opera Android Full support 19Safari iOS Full support 8Samsung Internet Android Full support 2.0nodejs Full support 0.12
resolve()Chrome Full support 32Edge Full support 12Firefox Full support 29IE No support NoOpera Full support 19Safari Full support 8WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29Opera Android Full support 19Safari iOS Full support 8Samsung Internet Android Full support 2.0nodejs Full support 0.12
then()Chrome Full support 32Edge Full support 12Firefox Full support 29IE No support NoOpera Full support 19Safari Full support 8WebView Android Full support 4.4.3Chrome Android Full support 32Firefox Android Full support 29Opera Android Full support 19Safari iOS Full support 8Samsung Internet Android Full support 2.0nodejs Full support 0.12

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No support
See implementation notes.
See implementation notes.

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