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nexedi
gitlab-ce
Commits
6801321c
Commit
6801321c
authored
Nov 15, 2016
by
Filipa Lacerda
Browse files
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Plain Diff
Adds es6-promise polyfill
Adds changelog
parent
37abb20c
Changes
3
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Showing
3 changed files
with
1164 additions
and
0 deletions
+1164
-0
app/assets/javascripts/application.js
app/assets/javascripts/application.js
+1
-0
changelogs/unreleased/24492-promise-polyfill.yml
changelogs/unreleased/24492-promise-polyfill.yml
+4
-0
vendor/assets/javascripts/es6-promise.auto.js
vendor/assets/javascripts/es6-promise.auto.js
+1159
-0
No files found.
app/assets/javascripts/application.js
View file @
6801321c
...
...
@@ -53,6 +53,7 @@
/*= require_directory ./u2f */
/*= require_directory . */
/*= require fuzzaldrin-plus */
/*= require es6-promise.auto */
(
function
()
{
document
.
addEventListener
(
'
page:fetch
'
,
gl
.
utils
.
cleanupBeforeFetch
);
...
...
changelogs/unreleased/24492-promise-polyfill.yml
0 → 100644
View file @
6801321c
---
title
:
Adds es6-promise Polyfill
merge_request
:
7482
author
:
vendor/assets/javascripts/es6-promise.auto.js
0 → 100644
View file @
6801321c
/*!
* @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 4.0.5
*/
(
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
)
{
return
typeof
x
===
'
function
'
||
typeof
x
===
'
object
'
&&
x
!==
null
;
}
function
isFunction
(
x
)
{
return
typeof
x
===
'
function
'
;
}
var
_isArray
=
undefined
;
if
(
!
Array
.
isArray
)
{
_isArray
=
function
(
x
)
{
return
Object
.
prototype
.
toString
.
call
(
x
)
===
'
[object Array]
'
;
};
}
else
{
_isArray
=
Array
.
isArray
;
}
var
isArray
=
_isArray
;
var
len
=
0
;
var
vertxNext
=
undefined
;
var
customSchedulerFn
=
undefined
;
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
r
=
require
;
var
vertx
=
r
(
'
vertx
'
);
vertxNext
=
vertx
.
runOnLoop
||
vertx
.
runOnContext
;
return
useVertxTimer
();
}
catch
(
e
)
{
return
useSetTimeout
();
}
}
var
scheduleFlush
=
undefined
;
// 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
_arguments
=
arguments
;
var
parent
=
this
;
var
child
=
new
this
.
constructor
(
noop
);
if
(
child
[
PROMISE_ID
]
===
undefined
)
{
makePromise
(
child
);
}
var
_state
=
parent
.
_state
;
if
(
_state
)
{
(
function
()
{
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
(
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
(
16
);
function
noop
()
{}
var
PENDING
=
void
0
;
var
FULFILLED
=
1
;
var
REJECTED
=
2
;
var
GET_THEN_ERROR
=
new
ErrorObject
();
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
getThen
(
promise
)
{
try
{
return
promise
.
then
;
}
catch
(
error
)
{
GET_THEN_ERROR
.
error
=
error
;
return
GET_THEN_ERROR
;
}
}
function
tryThen
(
then
,
value
,
fulfillmentHandler
,
rejectionHandler
)
{
try
{
then
.
call
(
value
,
fulfillmentHandler
,
rejectionHandler
);
}
catch
(
e
)
{
return
e
;
}
}
function
handleForeignThenable
(
promise
,
thenable
,
then
)
{
asap
(
function
(
promise
)
{
var
sealed
=
false
;
var
error
=
tryThen
(
then
,
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$$
)
{
if
(
maybeThenable
.
constructor
===
promise
.
constructor
&&
then$$
===
then
&&
maybeThenable
.
constructor
.
resolve
===
resolve
)
{
handleOwnThenable
(
promise
,
maybeThenable
);
}
else
{
if
(
then$$
===
GET_THEN_ERROR
)
{
_reject
(
promise
,
GET_THEN_ERROR
.
error
);
}
else
if
(
then$$
===
undefined
)
{
fulfill
(
promise
,
maybeThenable
);
}
else
if
(
isFunction
(
then$$
))
{
handleForeignThenable
(
promise
,
maybeThenable
,
then$$
);
}
else
{
fulfill
(
promise
,
maybeThenable
);
}
}
}
function
_resolve
(
promise
,
value
)
{
if
(
promise
===
value
)
{
_reject
(
promise
,
selfFulfillment
());
}
else
if
(
objectOrFunction
(
value
))
{
handleMaybeThenable
(
promise
,
value
,
getThen
(
value
));
}
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
=
undefined
,
callback
=
undefined
,
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
ErrorObject
()
{
this
.
error
=
null
;
}
var
TRY_CATCH_ERROR
=
new
ErrorObject
();
function
tryCatch
(
callback
,
detail
)
{
try
{
return
callback
(
detail
);
}
catch
(
e
)
{
TRY_CATCH_ERROR
.
error
=
e
;
return
TRY_CATCH_ERROR
;
}
}
function
invokeCallback
(
settled
,
promise
,
callback
,
detail
)
{
var
hasCallback
=
isFunction
(
callback
),
value
=
undefined
,
error
=
undefined
,
succeeded
=
undefined
,
failed
=
undefined
;
if
(
hasCallback
)
{
value
=
tryCatch
(
callback
,
detail
);
if
(
value
===
TRY_CATCH_ERROR
)
{
failed
=
true
;
error
=
value
.
error
;
value
=
null
;
}
else
{
succeeded
=
true
;
}
if
(
promise
===
value
)
{
_reject
(
promise
,
cannotReturnOwn
());
return
;
}
}
else
{
value
=
detail
;
succeeded
=
true
;
}
if
(
promise
.
_state
!==
PENDING
)
{
// noop
}
else
if
(
hasCallback
&&
succeeded
)
{
_resolve
(
promise
,
value
);
}
else
if
(
failed
)
{
_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
Enumerator
(
Constructor
,
input
)
{
this
.
_instanceConstructor
=
Constructor
;
this
.
promise
=
new
Constructor
(
noop
);
if
(
!
this
.
promise
[
PROMISE_ID
])
{
makePromise
(
this
.
promise
);
}
if
(
isArray
(
input
))
{
this
.
_input
=
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
();
if
(
this
.
_remaining
===
0
)
{
fulfill
(
this
.
promise
,
this
.
_result
);
}
}
}
else
{
_reject
(
this
.
promise
,
validationError
());
}
}
function
validationError
()
{
return
new
Error
(
'
Array Methods must be provided an Array
'
);
};
Enumerator
.
prototype
.
_enumerate
=
function
()
{
var
length
=
this
.
length
;
var
_input
=
this
.
_input
;
for
(
var
i
=
0
;
this
.
_state
===
PENDING
&&
i
<
length
;
i
++
)
{
this
.
_eachEntry
(
_input
[
i
],
i
);
}
};
Enumerator
.
prototype
.
_eachEntry
=
function
(
entry
,
i
)
{
var
c
=
this
.
_instanceConstructor
;
var
resolve$$
=
c
.
resolve
;
if
(
resolve$$
===
resolve
)
{
var
_then
=
getThen
(
entry
);
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
)
{
var
promise
=
new
c
(
noop
);
handleMaybeThenable
(
promise
,
entry
,
_then
);
this
.
_willSettleAt
(
promise
,
i
);
}
else
{
this
.
_willSettleAt
(
new
c
(
function
(
resolve$$
)
{
return
resolve$$
(
entry
);
}),
i
);
}
}
else
{
this
.
_willSettleAt
(
resolve$$
(
entry
),
i
);
}
};
Enumerator
.
prototype
.
_settledAt
=
function
(
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
(
promise
,
i
)
{
var
enumerator
=
this
;
subscribe
(
promise
,
undefined
,
function
(
value
)
{
return
enumerator
.
_settledAt
(
FULFILLED
,
i
,
value
);
},
function
(
reason
)
{
return
enumerator
.
_settledAt
(
REJECTED
,
i
,
reason
);
});
};
/**
`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
(
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
*/
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
();
}
}
Promise
.
all
=
all
;
Promise
.
race
=
race
;
Promise
.
resolve
=
resolve
;
Promise
.
reject
=
reject
;
Promise
.
_setScheduler
=
setScheduler
;
Promise
.
_setAsap
=
setAsap
;
Promise
.
_asap
=
asap
;
Promise
.
prototype
=
{
constructor
:
Promise
,
/**
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}
*/
then
:
then
,
/**
`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}
*/
'
catch
'
:
function
_catch
(
onRejection
)
{
return
this
.
then
(
null
,
onRejection
);
}
};
function
polyfill
()
{
var
local
=
undefined
;
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
;
}
// Strange compat..
Promise
.
polyfill
=
polyfill
;
Promise
.
Promise
=
Promise
;
return
Promise
;
})));
ES6Promise
.
polyfill
();
//# sourceMappingURL=es6-promise.auto.map
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