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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* This is an approximate implementation of ES7's async-await pattern.
* see: https://github.com/tc39/ecmascript-asyncawait
*
* It allows for simple creation of async function and "tasks".
*
* For example:
*
* var myThinger = {
* doAsynThing: async(function*(url){
* var result = yield fetch(url);
* return process(result);
* });
* }
*
* And Task-like things can be created as follows:
*
* var myTask = async(function*{
* var result = yield fetch(url);
* return result;
* });
* //returns a promise
*
* myTask().then(doSomethingElse);
*
*/
(function(exports) {
"use strict";
function async(func, self) {
return function asyncFunction() {
const functionArgs = Array.from(arguments);
return new Promise(function(resolve, reject) {
var gen;
if (typeof func !== "function") {
reject(new TypeError("Expected a Function."));
}
//not a generator, wrap it.
if (func.constructor.name !== "GeneratorFunction") {
gen = (function*() {
return func.apply(self, functionArgs);
}());
} else {
gen = func.apply(self, functionArgs);
}
try {
step(gen.next(undefined));
} catch (err) {
reject(err);
}
function step({value, done}) {
if (done) {
return resolve(value);
}
if (value instanceof Promise) {
return value.then(
result => step(gen.next(result)),
error => {
try {
step(gen.throw(error));
} catch (err) {
throw err;
}
}
).catch(err => reject(err));
}
step(gen.next(value));
}
});
};
}
exports.async = async;
}(this || self));
|
