You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
1174 lines
28 KiB
1174 lines
28 KiB
/*! |
|
* @overview es6-promise - a tiny implementation of Promises/A+. |
|
* @copyright Copyright (c) 2014 Yehuda Katz, Tom Dale, Stefan Penner and contributors (Conversion to ES6 API by Jake Archibald) |
|
* @license Licensed under MIT license |
|
* See https://raw.githubusercontent.com/stefanpenner/es6-promise/master/LICENSE |
|
* @version v4.2.8+1e68dce6 |
|
*/ |
|
|
|
(function (global, factory) { |
|
typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() : |
|
typeof define === 'function' && define.amd ? define(factory) : |
|
(global.ES6Promise = factory()); |
|
}(this, (function () { 'use strict'; |
|
|
|
function objectOrFunction(x) { |
|
var type = typeof x; |
|
return x !== null && (type === 'object' || type === 'function'); |
|
} |
|
|
|
function isFunction(x) { |
|
return typeof x === 'function'; |
|
} |
|
|
|
|
|
|
|
var _isArray = void 0; |
|
if (Array.isArray) { |
|
_isArray = Array.isArray; |
|
} else { |
|
_isArray = function (x) { |
|
return Object.prototype.toString.call(x) === '[object Array]'; |
|
}; |
|
} |
|
|
|
var isArray = _isArray; |
|
|
|
var len = 0; |
|
var vertxNext = void 0; |
|
var customSchedulerFn = void 0; |
|
|
|
var asap = function asap(callback, arg) { |
|
queue[len] = callback; |
|
queue[len + 1] = arg; |
|
len += 2; |
|
if (len === 2) { |
|
// If len is 2, that means that we need to schedule an async flush. |
|
// If additional callbacks are queued before the queue is flushed, they |
|
// will be processed by this flush that we are scheduling. |
|
if (customSchedulerFn) { |
|
customSchedulerFn(flush); |
|
} else { |
|
scheduleFlush(); |
|
} |
|
} |
|
}; |
|
|
|
function setScheduler(scheduleFn) { |
|
customSchedulerFn = scheduleFn; |
|
} |
|
|
|
function setAsap(asapFn) { |
|
asap = asapFn; |
|
} |
|
|
|
var browserWindow = typeof window !== 'undefined' ? window : undefined; |
|
var browserGlobal = browserWindow || {}; |
|
var BrowserMutationObserver = browserGlobal.MutationObserver || browserGlobal.WebKitMutationObserver; |
|
var isNode = typeof self === 'undefined' && typeof process !== 'undefined' && {}.toString.call(process) === '[object process]'; |
|
|
|
// test for web worker but not in IE10 |
|
var isWorker = typeof Uint8ClampedArray !== 'undefined' && typeof importScripts !== 'undefined' && typeof MessageChannel !== 'undefined'; |
|
|
|
// node |
|
function useNextTick() { |
|
// node version 0.10.x displays a deprecation warning when nextTick is used recursively |
|
// see https://github.com/cujojs/when/issues/410 for details |
|
return function () { |
|
return process.nextTick(flush); |
|
}; |
|
} |
|
|
|
// vertx |
|
function useVertxTimer() { |
|
if (typeof vertxNext !== 'undefined') { |
|
return function () { |
|
vertxNext(flush); |
|
}; |
|
} |
|
|
|
return useSetTimeout(); |
|
} |
|
|
|
function useMutationObserver() { |
|
var iterations = 0; |
|
var observer = new BrowserMutationObserver(flush); |
|
var node = document.createTextNode(''); |
|
observer.observe(node, { characterData: true }); |
|
|
|
return function () { |
|
node.data = iterations = ++iterations % 2; |
|
}; |
|
} |
|
|
|
// web worker |
|
function useMessageChannel() { |
|
var channel = new MessageChannel(); |
|
channel.port1.onmessage = flush; |
|
return function () { |
|
return channel.port2.postMessage(0); |
|
}; |
|
} |
|
|
|
function useSetTimeout() { |
|
// Store setTimeout reference so es6-promise will be unaffected by |
|
// other code modifying setTimeout (like sinon.useFakeTimers()) |
|
var globalSetTimeout = setTimeout; |
|
return function () { |
|
return globalSetTimeout(flush, 1); |
|
}; |
|
} |
|
|
|
var queue = new Array(1000); |
|
function flush() { |
|
for (var i = 0; i < len; i += 2) { |
|
var callback = queue[i]; |
|
var arg = queue[i + 1]; |
|
|
|
callback(arg); |
|
|
|
queue[i] = undefined; |
|
queue[i + 1] = undefined; |
|
} |
|
|
|
len = 0; |
|
} |
|
|
|
function attemptVertx() { |
|
try { |
|
var vertx = Function('return this')().require('vertx'); |
|
vertxNext = vertx.runOnLoop || vertx.runOnContext; |
|
return useVertxTimer(); |
|
} catch (e) { |
|
return useSetTimeout(); |
|
} |
|
} |
|
|
|
var scheduleFlush = void 0; |
|
// Decide what async method to use to triggering processing of queued callbacks: |
|
if (isNode) { |
|
scheduleFlush = useNextTick(); |
|
} else if (BrowserMutationObserver) { |
|
scheduleFlush = useMutationObserver(); |
|
} else if (isWorker) { |
|
scheduleFlush = useMessageChannel(); |
|
} else if (browserWindow === undefined && typeof require === 'function') { |
|
scheduleFlush = attemptVertx(); |
|
} else { |
|
scheduleFlush = useSetTimeout(); |
|
} |
|
|
|
function then(onFulfillment, onRejection) { |
|
var parent = this; |
|
|
|
var child = new this.constructor(noop); |
|
|
|
if (child[PROMISE_ID] === undefined) { |
|
makePromise(child); |
|
} |
|
|
|
var _state = parent._state; |
|
|
|
|
|
if (_state) { |
|
var callback = arguments[_state - 1]; |
|
asap(function () { |
|
return invokeCallback(_state, child, callback, parent._result); |
|
}); |
|
} else { |
|
subscribe(parent, child, onFulfillment, onRejection); |
|
} |
|
|
|
return child; |
|
} |
|
|
|
/** |
|
`Promise.resolve` returns a promise that will become resolved with the |
|
passed `value`. It is shorthand for the following: |
|
|
|
```javascript |
|
let promise = new Promise(function(resolve, reject){ |
|
resolve(1); |
|
}); |
|
|
|
promise.then(function(value){ |
|
// value === 1 |
|
}); |
|
``` |
|
|
|
Instead of writing the above, your code now simply becomes the following: |
|
|
|
```javascript |
|
let promise = Promise.resolve(1); |
|
|
|
promise.then(function(value){ |
|
// value === 1 |
|
}); |
|
``` |
|
|
|
@method resolve |
|
@static |
|
@param {Any} value value that the returned promise will be resolved with |
|
Useful for tooling. |
|
@return {Promise} a promise that will become fulfilled with the given |
|
`value` |
|
*/ |
|
function resolve$1(object) { |
|
/*jshint validthis:true */ |
|
var Constructor = this; |
|
|
|
if (object && typeof object === 'object' && object.constructor === Constructor) { |
|
return object; |
|
} |
|
|
|
var promise = new Constructor(noop); |
|
resolve(promise, object); |
|
return promise; |
|
} |
|
|
|
var PROMISE_ID = Math.random().toString(36).substring(2); |
|
|
|
function noop() {} |
|
|
|
var PENDING = void 0; |
|
var FULFILLED = 1; |
|
var REJECTED = 2; |
|
|
|
function selfFulfillment() { |
|
return new TypeError("You cannot resolve a promise with itself"); |
|
} |
|
|
|
function cannotReturnOwn() { |
|
return new TypeError('A promises callback cannot return that same promise.'); |
|
} |
|
|
|
function tryThen(then$$1, value, fulfillmentHandler, rejectionHandler) { |
|
try { |
|
then$$1.call(value, fulfillmentHandler, rejectionHandler); |
|
} catch (e) { |
|
return e; |
|
} |
|
} |
|
|
|
function handleForeignThenable(promise, thenable, then$$1) { |
|
asap(function (promise) { |
|
var sealed = false; |
|
var error = tryThen(then$$1, thenable, function (value) { |
|
if (sealed) { |
|
return; |
|
} |
|
sealed = true; |
|
if (thenable !== value) { |
|
resolve(promise, value); |
|
} else { |
|
fulfill(promise, value); |
|
} |
|
}, function (reason) { |
|
if (sealed) { |
|
return; |
|
} |
|
sealed = true; |
|
|
|
reject(promise, reason); |
|
}, 'Settle: ' + (promise._label || ' unknown promise')); |
|
|
|
if (!sealed && error) { |
|
sealed = true; |
|
reject(promise, error); |
|
} |
|
}, promise); |
|
} |
|
|
|
function handleOwnThenable(promise, thenable) { |
|
if (thenable._state === FULFILLED) { |
|
fulfill(promise, thenable._result); |
|
} else if (thenable._state === REJECTED) { |
|
reject(promise, thenable._result); |
|
} else { |
|
subscribe(thenable, undefined, function (value) { |
|
return resolve(promise, value); |
|
}, function (reason) { |
|
return reject(promise, reason); |
|
}); |
|
} |
|
} |
|
|
|
function handleMaybeThenable(promise, maybeThenable, then$$1) { |
|
if (maybeThenable.constructor === promise.constructor && then$$1 === then && maybeThenable.constructor.resolve === resolve$1) { |
|
handleOwnThenable(promise, maybeThenable); |
|
} else { |
|
if (then$$1 === undefined) { |
|
fulfill(promise, maybeThenable); |
|
} else if (isFunction(then$$1)) { |
|
handleForeignThenable(promise, maybeThenable, then$$1); |
|
} else { |
|
fulfill(promise, maybeThenable); |
|
} |
|
} |
|
} |
|
|
|
function resolve(promise, value) { |
|
if (promise === value) { |
|
reject(promise, selfFulfillment()); |
|
} else if (objectOrFunction(value)) { |
|
var then$$1 = void 0; |
|
try { |
|
then$$1 = value.then; |
|
} catch (error) { |
|
reject(promise, error); |
|
return; |
|
} |
|
handleMaybeThenable(promise, value, then$$1); |
|
} else { |
|
fulfill(promise, value); |
|
} |
|
} |
|
|
|
function publishRejection(promise) { |
|
if (promise._onerror) { |
|
promise._onerror(promise._result); |
|
} |
|
|
|
publish(promise); |
|
} |
|
|
|
function fulfill(promise, value) { |
|
if (promise._state !== PENDING) { |
|
return; |
|
} |
|
|
|
promise._result = value; |
|
promise._state = FULFILLED; |
|
|
|
if (promise._subscribers.length !== 0) { |
|
asap(publish, promise); |
|
} |
|
} |
|
|
|
function reject(promise, reason) { |
|
if (promise._state !== PENDING) { |
|
return; |
|
} |
|
promise._state = REJECTED; |
|
promise._result = reason; |
|
|
|
asap(publishRejection, promise); |
|
} |
|
|
|
function subscribe(parent, child, onFulfillment, onRejection) { |
|
var _subscribers = parent._subscribers; |
|
var length = _subscribers.length; |
|
|
|
|
|
parent._onerror = null; |
|
|
|
_subscribers[length] = child; |
|
_subscribers[length + FULFILLED] = onFulfillment; |
|
_subscribers[length + REJECTED] = onRejection; |
|
|
|
if (length === 0 && parent._state) { |
|
asap(publish, parent); |
|
} |
|
} |
|
|
|
function publish(promise) { |
|
var subscribers = promise._subscribers; |
|
var settled = promise._state; |
|
|
|
if (subscribers.length === 0) { |
|
return; |
|
} |
|
|
|
var child = void 0, |
|
callback = void 0, |
|
detail = promise._result; |
|
|
|
for (var i = 0; i < subscribers.length; i += 3) { |
|
child = subscribers[i]; |
|
callback = subscribers[i + settled]; |
|
|
|
if (child) { |
|
invokeCallback(settled, child, callback, detail); |
|
} else { |
|
callback(detail); |
|
} |
|
} |
|
|
|
promise._subscribers.length = 0; |
|
} |
|
|
|
function invokeCallback(settled, promise, callback, detail) { |
|
var hasCallback = isFunction(callback), |
|
value = void 0, |
|
error = void 0, |
|
succeeded = true; |
|
|
|
if (hasCallback) { |
|
try { |
|
value = callback(detail); |
|
} catch (e) { |
|
succeeded = false; |
|
error = e; |
|
} |
|
|
|
if (promise === value) { |
|
reject(promise, cannotReturnOwn()); |
|
return; |
|
} |
|
} else { |
|
value = detail; |
|
} |
|
|
|
if (promise._state !== PENDING) { |
|
// noop |
|
} else if (hasCallback && succeeded) { |
|
resolve(promise, value); |
|
} else if (succeeded === false) { |
|
reject(promise, error); |
|
} else if (settled === FULFILLED) { |
|
fulfill(promise, value); |
|
} else if (settled === REJECTED) { |
|
reject(promise, value); |
|
} |
|
} |
|
|
|
function initializePromise(promise, resolver) { |
|
try { |
|
resolver(function resolvePromise(value) { |
|
resolve(promise, value); |
|
}, function rejectPromise(reason) { |
|
reject(promise, reason); |
|
}); |
|
} catch (e) { |
|
reject(promise, e); |
|
} |
|
} |
|
|
|
var id = 0; |
|
function nextId() { |
|
return id++; |
|
} |
|
|
|
function makePromise(promise) { |
|
promise[PROMISE_ID] = id++; |
|
promise._state = undefined; |
|
promise._result = undefined; |
|
promise._subscribers = []; |
|
} |
|
|
|
function validationError() { |
|
return new Error('Array Methods must be provided an Array'); |
|
} |
|
|
|
var Enumerator = function () { |
|
function Enumerator(Constructor, input) { |
|
this._instanceConstructor = Constructor; |
|
this.promise = new Constructor(noop); |
|
|
|
if (!this.promise[PROMISE_ID]) { |
|
makePromise(this.promise); |
|
} |
|
|
|
if (isArray(input)) { |
|
this.length = input.length; |
|
this._remaining = input.length; |
|
|
|
this._result = new Array(this.length); |
|
|
|
if (this.length === 0) { |
|
fulfill(this.promise, this._result); |
|
} else { |
|
this.length = this.length || 0; |
|
this._enumerate(input); |
|
if (this._remaining === 0) { |
|
fulfill(this.promise, this._result); |
|
} |
|
} |
|
} else { |
|
reject(this.promise, validationError()); |
|
} |
|
} |
|
|
|
Enumerator.prototype._enumerate = function _enumerate(input) { |
|
for (var i = 0; this._state === PENDING && i < input.length; i++) { |
|
this._eachEntry(input[i], i); |
|
} |
|
}; |
|
|
|
Enumerator.prototype._eachEntry = function _eachEntry(entry, i) { |
|
var c = this._instanceConstructor; |
|
var resolve$$1 = c.resolve; |
|
|
|
|
|
if (resolve$$1 === resolve$1) { |
|
var _then = void 0; |
|
var error = void 0; |
|
var didError = false; |
|
try { |
|
_then = entry.then; |
|
} catch (e) { |
|
didError = true; |
|
error = e; |
|
} |
|
|
|
if (_then === then && entry._state !== PENDING) { |
|
this._settledAt(entry._state, i, entry._result); |
|
} else if (typeof _then !== 'function') { |
|
this._remaining--; |
|
this._result[i] = entry; |
|
} else if (c === Promise$1) { |
|
var promise = new c(noop); |
|
if (didError) { |
|
reject(promise, error); |
|
} else { |
|
handleMaybeThenable(promise, entry, _then); |
|
} |
|
this._willSettleAt(promise, i); |
|
} else { |
|
this._willSettleAt(new c(function (resolve$$1) { |
|
return resolve$$1(entry); |
|
}), i); |
|
} |
|
} else { |
|
this._willSettleAt(resolve$$1(entry), i); |
|
} |
|
}; |
|
|
|
Enumerator.prototype._settledAt = function _settledAt(state, i, value) { |
|
var promise = this.promise; |
|
|
|
|
|
if (promise._state === PENDING) { |
|
this._remaining--; |
|
|
|
if (state === REJECTED) { |
|
reject(promise, value); |
|
} else { |
|
this._result[i] = value; |
|
} |
|
} |
|
|
|
if (this._remaining === 0) { |
|
fulfill(promise, this._result); |
|
} |
|
}; |
|
|
|
Enumerator.prototype._willSettleAt = function _willSettleAt(promise, i) { |
|
var enumerator = this; |
|
|
|
subscribe(promise, undefined, function (value) { |
|
return enumerator._settledAt(FULFILLED, i, value); |
|
}, function (reason) { |
|
return enumerator._settledAt(REJECTED, i, reason); |
|
}); |
|
}; |
|
|
|
return Enumerator; |
|
}(); |
|
|
|
/** |
|
`Promise.all` accepts an array of promises, and returns a new promise which |
|
is fulfilled with an array of fulfillment values for the passed promises, or |
|
rejected with the reason of the first passed promise to be rejected. It casts all |
|
elements of the passed iterable to promises as it runs this algorithm. |
|
|
|
Example: |
|
|
|
```javascript |
|
let promise1 = resolve(1); |
|
let promise2 = resolve(2); |
|
let promise3 = resolve(3); |
|
let promises = [ promise1, promise2, promise3 ]; |
|
|
|
Promise.all(promises).then(function(array){ |
|
// The array here would be [ 1, 2, 3 ]; |
|
}); |
|
``` |
|
|
|
If any of the `promises` given to `all` are rejected, the first promise |
|
that is rejected will be given as an argument to the returned promises's |
|
rejection handler. For example: |
|
|
|
Example: |
|
|
|
```javascript |
|
let promise1 = resolve(1); |
|
let promise2 = reject(new Error("2")); |
|
let promise3 = reject(new Error("3")); |
|
let promises = [ promise1, promise2, promise3 ]; |
|
|
|
Promise.all(promises).then(function(array){ |
|
// Code here never runs because there are rejected promises! |
|
}, function(error) { |
|
// error.message === "2" |
|
}); |
|
``` |
|
|
|
@method all |
|
@static |
|
@param {Array} entries array of promises |
|
@param {String} label optional string for labeling the promise. |
|
Useful for tooling. |
|
@return {Promise} promise that is fulfilled when all `promises` have been |
|
fulfilled, or rejected if any of them become rejected. |
|
@static |
|
*/ |
|
function all(entries) { |
|
return new Enumerator(this, entries).promise; |
|
} |
|
|
|
/** |
|
`Promise.race` returns a new promise which is settled in the same way as the |
|
first passed promise to settle. |
|
|
|
Example: |
|
|
|
```javascript |
|
let promise1 = new Promise(function(resolve, reject){ |
|
setTimeout(function(){ |
|
resolve('promise 1'); |
|
}, 200); |
|
}); |
|
|
|
let promise2 = new Promise(function(resolve, reject){ |
|
setTimeout(function(){ |
|
resolve('promise 2'); |
|
}, 100); |
|
}); |
|
|
|
Promise.race([promise1, promise2]).then(function(result){ |
|
// result === 'promise 2' because it was resolved before promise1 |
|
// was resolved. |
|
}); |
|
``` |
|
|
|
`Promise.race` is deterministic in that only the state of the first |
|
settled promise matters. For example, even if other promises given to the |
|
`promises` array argument are resolved, but the first settled promise has |
|
become rejected before the other promises became fulfilled, the returned |
|
promise will become rejected: |
|
|
|
```javascript |
|
let promise1 = new Promise(function(resolve, reject){ |
|
setTimeout(function(){ |
|
resolve('promise 1'); |
|
}, 200); |
|
}); |
|
|
|
let promise2 = new Promise(function(resolve, reject){ |
|
setTimeout(function(){ |
|
reject(new Error('promise 2')); |
|
}, 100); |
|
}); |
|
|
|
Promise.race([promise1, promise2]).then(function(result){ |
|
// Code here never runs |
|
}, function(reason){ |
|
// reason.message === 'promise 2' because promise 2 became rejected before |
|
// promise 1 became fulfilled |
|
}); |
|
``` |
|
|
|
An example real-world use case is implementing timeouts: |
|
|
|
```javascript |
|
Promise.race([ajax('foo.json'), timeout(5000)]) |
|
``` |
|
|
|
@method race |
|
@static |
|
@param {Array} promises array of promises to observe |
|
Useful for tooling. |
|
@return {Promise} a promise which settles in the same way as the first passed |
|
promise to settle. |
|
*/ |
|
function race(entries) { |
|
/*jshint validthis:true */ |
|
var Constructor = this; |
|
|
|
if (!isArray(entries)) { |
|
return new Constructor(function (_, reject) { |
|
return reject(new TypeError('You must pass an array to race.')); |
|
}); |
|
} else { |
|
return new Constructor(function (resolve, reject) { |
|
var length = entries.length; |
|
for (var i = 0; i < length; i++) { |
|
Constructor.resolve(entries[i]).then(resolve, reject); |
|
} |
|
}); |
|
} |
|
} |
|
|
|
/** |
|
`Promise.reject` returns a promise rejected with the passed `reason`. |
|
It is shorthand for the following: |
|
|
|
```javascript |
|
let promise = new Promise(function(resolve, reject){ |
|
reject(new Error('WHOOPS')); |
|
}); |
|
|
|
promise.then(function(value){ |
|
// Code here doesn't run because the promise is rejected! |
|
}, function(reason){ |
|
// reason.message === 'WHOOPS' |
|
}); |
|
``` |
|
|
|
Instead of writing the above, your code now simply becomes the following: |
|
|
|
```javascript |
|
let promise = Promise.reject(new Error('WHOOPS')); |
|
|
|
promise.then(function(value){ |
|
// Code here doesn't run because the promise is rejected! |
|
}, function(reason){ |
|
// reason.message === 'WHOOPS' |
|
}); |
|
``` |
|
|
|
@method reject |
|
@static |
|
@param {Any} reason value that the returned promise will be rejected with. |
|
Useful for tooling. |
|
@return {Promise} a promise rejected with the given `reason`. |
|
*/ |
|
function reject$1(reason) { |
|
/*jshint validthis:true */ |
|
var Constructor = this; |
|
var promise = new Constructor(noop); |
|
reject(promise, reason); |
|
return promise; |
|
} |
|
|
|
function needsResolver() { |
|
throw new TypeError('You must pass a resolver function as the first argument to the promise constructor'); |
|
} |
|
|
|
function needsNew() { |
|
throw new TypeError("Failed to construct 'Promise': Please use the 'new' operator, this object constructor cannot be called as a function."); |
|
} |
|
|
|
/** |
|
Promise objects represent the eventual result of an asynchronous operation. The |
|
primary way of interacting with a promise is through its `then` method, which |
|
registers callbacks to receive either a promise's eventual value or the reason |
|
why the promise cannot be fulfilled. |
|
|
|
Terminology |
|
----------- |
|
|
|
- `promise` is an object or function with a `then` method whose behavior conforms to this specification. |
|
- `thenable` is an object or function that defines a `then` method. |
|
- `value` is any legal JavaScript value (including undefined, a thenable, or a promise). |
|
- `exception` is a value that is thrown using the throw statement. |
|
- `reason` is a value that indicates why a promise was rejected. |
|
- `settled` the final resting state of a promise, fulfilled or rejected. |
|
|
|
A promise can be in one of three states: pending, fulfilled, or rejected. |
|
|
|
Promises that are fulfilled have a fulfillment value and are in the fulfilled |
|
state. Promises that are rejected have a rejection reason and are in the |
|
rejected state. A fulfillment value is never a thenable. |
|
|
|
Promises can also be said to *resolve* a value. If this value is also a |
|
promise, then the original promise's settled state will match the value's |
|
settled state. So a promise that *resolves* a promise that rejects will |
|
itself reject, and a promise that *resolves* a promise that fulfills will |
|
itself fulfill. |
|
|
|
|
|
Basic Usage: |
|
------------ |
|
|
|
```js |
|
let promise = new Promise(function(resolve, reject) { |
|
// on success |
|
resolve(value); |
|
|
|
// on failure |
|
reject(reason); |
|
}); |
|
|
|
promise.then(function(value) { |
|
// on fulfillment |
|
}, function(reason) { |
|
// on rejection |
|
}); |
|
``` |
|
|
|
Advanced Usage: |
|
--------------- |
|
|
|
Promises shine when abstracting away asynchronous interactions such as |
|
`XMLHttpRequest`s. |
|
|
|
```js |
|
function getJSON(url) { |
|
return new Promise(function(resolve, reject){ |
|
let xhr = new XMLHttpRequest(); |
|
|
|
xhr.open('GET', url); |
|
xhr.onreadystatechange = handler; |
|
xhr.responseType = 'json'; |
|
xhr.setRequestHeader('Accept', 'application/json'); |
|
xhr.send(); |
|
|
|
function handler() { |
|
if (this.readyState === this.DONE) { |
|
if (this.status === 200) { |
|
resolve(this.response); |
|
} else { |
|
reject(new Error('getJSON: `' + url + '` failed with status: [' + this.status + ']')); |
|
} |
|
} |
|
}; |
|
}); |
|
} |
|
|
|
getJSON('/posts.json').then(function(json) { |
|
// on fulfillment |
|
}, function(reason) { |
|
// on rejection |
|
}); |
|
``` |
|
|
|
Unlike callbacks, promises are great composable primitives. |
|
|
|
```js |
|
Promise.all([ |
|
getJSON('/posts'), |
|
getJSON('/comments') |
|
]).then(function(values){ |
|
values[0] // => postsJSON |
|
values[1] // => commentsJSON |
|
|
|
return values; |
|
}); |
|
``` |
|
|
|
@class Promise |
|
@param {Function} resolver |
|
Useful for tooling. |
|
@constructor |
|
*/ |
|
|
|
var Promise$1 = function () { |
|
function Promise(resolver) { |
|
this[PROMISE_ID] = nextId(); |
|
this._result = this._state = undefined; |
|
this._subscribers = []; |
|
|
|
if (noop !== resolver) { |
|
typeof resolver !== 'function' && needsResolver(); |
|
this instanceof Promise ? initializePromise(this, resolver) : needsNew(); |
|
} |
|
} |
|
|
|
/** |
|
The primary way of interacting with a promise is through its `then` method, |
|
which registers callbacks to receive either a promise's eventual value or the |
|
reason why the promise cannot be fulfilled. |
|
```js |
|
findUser().then(function(user){ |
|
// user is available |
|
}, function(reason){ |
|
// user is unavailable, and you are given the reason why |
|
}); |
|
``` |
|
Chaining |
|
-------- |
|
The return value of `then` is itself a promise. This second, 'downstream' |
|
promise is resolved with the return value of the first promise's fulfillment |
|
or rejection handler, or rejected if the handler throws an exception. |
|
```js |
|
findUser().then(function (user) { |
|
return user.name; |
|
}, function (reason) { |
|
return 'default name'; |
|
}).then(function (userName) { |
|
// If `findUser` fulfilled, `userName` will be the user's name, otherwise it |
|
// will be `'default name'` |
|
}); |
|
findUser().then(function (user) { |
|
throw new Error('Found user, but still unhappy'); |
|
}, function (reason) { |
|
throw new Error('`findUser` rejected and we're unhappy'); |
|
}).then(function (value) { |
|
// never reached |
|
}, function (reason) { |
|
// if `findUser` fulfilled, `reason` will be 'Found user, but still unhappy'. |
|
// If `findUser` rejected, `reason` will be '`findUser` rejected and we're unhappy'. |
|
}); |
|
``` |
|
If the downstream promise does not specify a rejection handler, rejection reasons will be propagated further downstream. |
|
```js |
|
findUser().then(function (user) { |
|
throw new PedagogicalException('Upstream error'); |
|
}).then(function (value) { |
|
// never reached |
|
}).then(function (value) { |
|
// never reached |
|
}, function (reason) { |
|
// The `PedgagocialException` is propagated all the way down to here |
|
}); |
|
``` |
|
Assimilation |
|
------------ |
|
Sometimes the value you want to propagate to a downstream promise can only be |
|
retrieved asynchronously. This can be achieved by returning a promise in the |
|
fulfillment or rejection handler. The downstream promise will then be pending |
|
until the returned promise is settled. This is called *assimilation*. |
|
```js |
|
findUser().then(function (user) { |
|
return findCommentsByAuthor(user); |
|
}).then(function (comments) { |
|
// The user's comments are now available |
|
}); |
|
``` |
|
If the assimliated promise rejects, then the downstream promise will also reject. |
|
```js |
|
findUser().then(function (user) { |
|
return findCommentsByAuthor(user); |
|
}).then(function (comments) { |
|
// If `findCommentsByAuthor` fulfills, we'll have the value here |
|
}, function (reason) { |
|
// If `findCommentsByAuthor` rejects, we'll have the reason here |
|
}); |
|
``` |
|
Simple Example |
|
-------------- |
|
Synchronous Example |
|
```javascript |
|
let result; |
|
try { |
|
result = findResult(); |
|
// success |
|
} catch(reason) { |
|
// failure |
|
} |
|
``` |
|
Errback Example |
|
```js |
|
findResult(function(result, err){ |
|
if (err) { |
|
// failure |
|
} else { |
|
// success |
|
} |
|
}); |
|
``` |
|
Promise Example; |
|
```javascript |
|
findResult().then(function(result){ |
|
// success |
|
}, function(reason){ |
|
// failure |
|
}); |
|
``` |
|
Advanced Example |
|
-------------- |
|
Synchronous Example |
|
```javascript |
|
let author, books; |
|
try { |
|
author = findAuthor(); |
|
books = findBooksByAuthor(author); |
|
// success |
|
} catch(reason) { |
|
// failure |
|
} |
|
``` |
|
Errback Example |
|
```js |
|
function foundBooks(books) { |
|
} |
|
function failure(reason) { |
|
} |
|
findAuthor(function(author, err){ |
|
if (err) { |
|
failure(err); |
|
// failure |
|
} else { |
|
try { |
|
findBoooksByAuthor(author, function(books, err) { |
|
if (err) { |
|
failure(err); |
|
} else { |
|
try { |
|
foundBooks(books); |
|
} catch(reason) { |
|
failure(reason); |
|
} |
|
} |
|
}); |
|
} catch(error) { |
|
failure(err); |
|
} |
|
// success |
|
} |
|
}); |
|
``` |
|
Promise Example; |
|
```javascript |
|
findAuthor(). |
|
then(findBooksByAuthor). |
|
then(function(books){ |
|
// found books |
|
}).catch(function(reason){ |
|
// something went wrong |
|
}); |
|
``` |
|
@method then |
|
@param {Function} onFulfilled |
|
@param {Function} onRejected |
|
Useful for tooling. |
|
@return {Promise} |
|
*/ |
|
|
|
/** |
|
`catch` is simply sugar for `then(undefined, onRejection)` which makes it the same |
|
as the catch block of a try/catch statement. |
|
```js |
|
function findAuthor(){ |
|
throw new Error('couldn't find that author'); |
|
} |
|
// synchronous |
|
try { |
|
findAuthor(); |
|
} catch(reason) { |
|
// something went wrong |
|
} |
|
// async with promises |
|
findAuthor().catch(function(reason){ |
|
// something went wrong |
|
}); |
|
``` |
|
@method catch |
|
@param {Function} onRejection |
|
Useful for tooling. |
|
@return {Promise} |
|
*/ |
|
|
|
|
|
Promise.prototype.catch = function _catch(onRejection) { |
|
return this.then(null, onRejection); |
|
}; |
|
|
|
/** |
|
`finally` will be invoked regardless of the promise's fate just as native |
|
try/catch/finally behaves |
|
|
|
Synchronous example: |
|
|
|
```js |
|
findAuthor() { |
|
if (Math.random() > 0.5) { |
|
throw new Error(); |
|
} |
|
return new Author(); |
|
} |
|
|
|
try { |
|
return findAuthor(); // succeed or fail |
|
} catch(error) { |
|
return findOtherAuther(); |
|
} finally { |
|
// always runs |
|
// doesn't affect the return value |
|
} |
|
``` |
|
|
|
Asynchronous example: |
|
|
|
```js |
|
findAuthor().catch(function(reason){ |
|
return findOtherAuther(); |
|
}).finally(function(){ |
|
// author was either found, or not |
|
}); |
|
``` |
|
|
|
@method finally |
|
@param {Function} callback |
|
@return {Promise} |
|
*/ |
|
|
|
|
|
Promise.prototype.finally = function _finally(callback) { |
|
var promise = this; |
|
var constructor = promise.constructor; |
|
|
|
if (isFunction(callback)) { |
|
return promise.then(function (value) { |
|
return constructor.resolve(callback()).then(function () { |
|
return value; |
|
}); |
|
}, function (reason) { |
|
return constructor.resolve(callback()).then(function () { |
|
throw reason; |
|
}); |
|
}); |
|
} |
|
|
|
return promise.then(callback, callback); |
|
}; |
|
|
|
return Promise; |
|
}(); |
|
|
|
Promise$1.prototype.then = then; |
|
Promise$1.all = all; |
|
Promise$1.race = race; |
|
Promise$1.resolve = resolve$1; |
|
Promise$1.reject = reject$1; |
|
Promise$1._setScheduler = setScheduler; |
|
Promise$1._setAsap = setAsap; |
|
Promise$1._asap = asap; |
|
|
|
/*global self*/ |
|
function polyfill() { |
|
var local = void 0; |
|
|
|
if (typeof global !== 'undefined') { |
|
local = global; |
|
} else if (typeof self !== 'undefined') { |
|
local = self; |
|
} else { |
|
try { |
|
local = Function('return this')(); |
|
} catch (e) { |
|
throw new Error('polyfill failed because global object is unavailable in this environment'); |
|
} |
|
} |
|
|
|
var P = local.Promise; |
|
|
|
if (P) { |
|
var promiseToString = null; |
|
try { |
|
promiseToString = Object.prototype.toString.call(P.resolve()); |
|
} catch (e) { |
|
// silently ignored |
|
} |
|
|
|
if (promiseToString === '[object Promise]' && !P.cast) { |
|
return; |
|
} |
|
} |
|
|
|
local.Promise = Promise$1; |
|
} |
|
|
|
// Strange compat.. |
|
Promise$1.polyfill = polyfill; |
|
Promise$1.Promise = Promise$1; |
|
|
|
return Promise$1; |
|
|
|
}))); |
|
|
|
|
|
|
|
//# sourceMappingURL=es6-promise.map
|
|
|