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