Module ringo/promise
Allows to work with deferred values that will be resolved in the future.
Class PromiseList
Deferred ()
Creates an object representing a deferred value. The deferred object has two properties: a promise object and a resolve() function.
The promise object can be used to register a callback to be invoked when the promise is eventually resolved.
The resolve function is used to resolve the promise as either fulfilled or failed.
Example
// --- sample output ---
// getDeferredValue() ...
// getDeferredValue() finished after 396 ms
// Resolved promise, got foo
// Total time: 2400 ms
const getDeferredValue = function () {
const deferred = new Deferred();
setTimeout(function() {
deferred.resolve("foo");
}, 2000);
return deferred;
};
const start = Date.now();
console.log("getDeferredValue() ... ");
const def = getDeferredValue();
console.log("getDeferredValue() finished after",
Date.now() - start, "ms");
def.promise.then(function(value) {
console.log("Resolved promise, got", value);
console.log("Total time: ", Date.now() - start, "ms");
});Deferred.prototype. promise
The promise object can be used to register a callback to be invoked when the promise is eventually resolved.
Deferred.prototype. resolve (result, isError)
Resolve the promise.
Parameters
| Object | result | the result or error value |
| Boolean | isError | if true the promise is resolved as failed |
Promise
A promise object. This class is not exported, create a deferred object to create a promise.
Promise.prototype. then (callback, errback)
Register callback and errback functions to be invoked when the promise is resolved.
Parameters
| Function | callback | called if the promise is resolved as fulfilled |
| Function | errback | called if the promise is resolved as failed |
Returns
| Object | a new promise that resolves to the return value of the callback or errback when it is called. |
Promise.prototype. wait (timeout)
Wait for the promise to be resolved.
Parameters
| Number | timeout | optional time in milliseconds to wait for. If timeout is undefined wait() blocks forever. |
Returns
| Object | the value if the promise is resolved as fulfilled |
Throws
PromiseList (promise...)
The PromiseList class allows to combine several promises into one.
It represents itself a promise that resolves to an array of objects,
each containing a value or error property with the value
or error of the corresponding promise argument.
A PromiseList resolves successfully even if some or all of the partial promises resolve to an error. It is the responsibility of the handler function to check each individual promise result.
Example
// --- sample output ---
// Done!
// { value: 'i am ok' }
// { value: 1 }
// { error: 'some error' }
let d1 = Deferred(), d2 = Deferred(), d3 = Deferred();
// PromiseList accepts a promise or deferred object
let list = PromiseList(d1.promise, d2, d3);
list.then(function(results) {
console.log("Done!");
results.forEach(function(result) {
console.dir(result);
});
}, function(error) {
console.error("Error :-(");
});
d2.resolve(1);
d3.resolve("some error", true);
d1.resolve("i am ok");Parameters
| Promise... | promise... | any number of promise arguments. |