Advanced control of JavaScript promises.
npm install promise-controller --saveimport PromiseController from 'promise-controller';
const pc = new PromiseController();
const promise = pc.call(() => startAsyncProcess());
// ...when async process done
pc.resolve('done');
// or
pc.reject();- Easy access to
resolve/rejectcallbacks - Re-use of existing promise while operation is pending
- Automatically reject after timeout
With bare Promise:
let resolve, reject;
const asyncOperation = setTimeout(() => Math.random() > 0.5 ? resolve() : reject(), 100);
const promise = new Promise((_resolve, _reject) => {
resolve = _resolve;
reject = _reject;
asyncOperation();
});With PromiseController:
const pc = new PromiseController();
const asyncOperation = setTimeout(() => Math.random() > 0.5 ? pc.resolve() : pc.reject(), 100);
const promise = pc.call(asyncOperation);With bare Promise:
let promise = null;
function connectToDb() {
if (!promise) {
promise = mongoClient.open();
}
return promise;
}With PromiseController:
const pc = new PromiseController();
function connectToDb() {
return pc.promise || pc.call(() => mongoClient.open());
}With bare Promise:
let resolve, timer;
const asyncOperation = setTimeout(() => {
resolve();
clearTimeout(timer);
}, 100);
const promise = new Promise((_resolve, _reject) => {
resolve = _resolve;
asyncOperation();
timer = setTimeout(() => _reject(), 50);
});With PromiseController:
const pc = new PromiseController({
timeout: 50
});
const asyncOperation = setTimeout(() => resolve(), 100);
const promise = pc.call(asyncOperation);- Options :
Object
Kind: global class
- PromiseController
- new PromiseController([options])
- instance
- .promise ⇒
Promise - .value ⇒
* - .isPending ⇒
Boolean - .isFulfilled ⇒
Boolean - .isRejected ⇒
Boolean - .isSettled ⇒
Boolean - .call([fn]) ⇒
Promise - .resolve([value])
- .reject([value])
- .reset()
- .configure(options)
- .promise ⇒
- static
Creates promise controller. Unlike original Promise, it does not immediately call any function.
Instead it has .call() method that calls provided function
and stores resolve / reject methods for future access.
| Param | Type |
|---|---|
| [options] | Options |
Returns promise itself.
Kind: instance property of PromiseController
Returns value with that promise was settled (fulfilled or rejected).
Kind: instance property of PromiseController
Returns true if promise is pending.
Kind: instance property of PromiseController
Returns true if promise is fulfilled.
Kind: instance property of PromiseController
Returns true if promise rejected.
Kind: instance property of PromiseController
Returns true if promise is fulfilled or rejected.
Kind: instance property of Pro
9299
miseController
Calls fn and returns promise OR just returns existing promise from previous call() if it is still pending.
To fulfill returned promise you should use
resolve / reject methods.
If fn itself returns promise, then external promise is attached to it and fulfills together.
If no fn passed - promiseController is initialized as well.
Kind: instance method of PromiseController
| Param | Type | Description |
|---|---|---|
| [fn] | function |
function to be called. |
Resolves pending promise with specified value.
Kind: instance method of PromiseController
| Param | Type |
|---|---|
| [value] | * |
Rejects pending promise with specified value.
Kind: instance method of PromiseController
| Param | Type |
|---|---|
| [value] | * |
Resets to initial state. If promise is pending it will be rejected with ResetError.
Kind: instance method of PromiseController
Re-assign one or more options.
Kind: instance method of PromiseController
| Param | Type |
|---|---|
| options | Options |
PromiseController.TimeoutError : TimeoutError
Error for rejection in case of timeout.
Kind: static property of PromiseController
PromiseController.ResetError : ResetError
Error for rejection in case of call .reset() while promise is pending.
Kind: static property of PromiseController
Kind: global typedef
Properties
| Name | Type | Default | Description |
|---|---|---|---|
| [timeout] | Number |
0 |
Timeout in ms after that promise will be rejected automatically. |
| [timeoutReason] | String | function |
Rejection reason for timeout. Promise will be rejected with TimeoutError and this message. The message can contain placeholder {timeout} for actual timeout value. If timeoutReason is a function, it will be evaluated and returned value will be used as message. |
|
| [resetReason] | String | function |
Rejection reason used when .reset() is called while promise is pending. Promise will be rejected with ResetError and this message. If resetReason is a function, it will be evaluated and returned value will be used as message. |
MIT @ Vitaliy Potapov