As Felix says, a promise is just another value to be yielded. However, there is a style of writing asynchronous code which makes use of yielded promises in a particular way. This involves a surrounding piece of code which invokes the generator, then waits for the yielded promise to resolve, and then and only then … Read more
The relevant specs are here: Promises/A+ point 2.2.4: onFulfilled or onRejected must not be called until the execution context stack contains only platform code. [3.1]. And note 3.1 (emphasis mine): Here “platform code” means engine, environment, and promise implementation code. In practice, this requirement ensures that onFulfilled and onRejected execute asynchronously, after the event loop … Read more
If you don’t care about the results, then it’s quick to whip one up: Promise.eachLimit = async (funcs, limit) => { let rest = funcs.slice(limit); await Promise.all(funcs.slice(0, limit).map(async func => { await func(); while (rest.length) { await rest.shift()(); } })); }; // Demo: var wait = ms => new Promise(resolve => setTimeout(resolve, ms)); async function … Read more
Yes, that will suffice. Promises are simple return values, which is their great benefit – in contrast to callbacks, where memoisation code would be horrible. You only might want to make sure that the memoized promise is uncancellable, if your promise library does support some kind of cancellation. Also notice that this form of memoisation … Read more
Good question. Let me start by one thing: Promises are not event emitters. Let me reiterate that, since it’s a misconception that comes a lot. Promises are not event emitters. With progression, they can be hacked into a form of crippled event emitter but at the end of the day. Promises are not event emitters. … Read more
Looks like you need a custom matcher. Depending on the version of Jasmine you are using: With Jasmine 1: this.addMatchers({ toBeIn: function(expected) { var possibilities = Array.isArray(expected) ? expected : [expected]; return possibilities.indexOf(this.actual) > -1; } }); With Jasmine 2: this.addMatchers({ toBeIn: function(util, customEqualityTesters) { return { compare: function(actual, expected) { var possibilities = Array.isArray(expected) … Read more
sort does not take an asynchronous callback. It expects a numeric value as the return value, not a promise for one; and it does return an array not a promise. There’s no way around this (though one could implement a custom asynchronous sorting algorithm – even a parallel one). But that’s pretty inefficient anyway. Doing … Read more
The thing that bothers me most is who is passing the Resolver and Reject function to a promise constructor ? Nobody. The functions are passed by the promise constructor. They are passed to the function which you pass as the first argument to the promise constructor.
You could have the property lazily set itself, something like: App.TopicItem = DS.Model.extend({ topic: DS.belongsTo(‘topic’), paddedPosition: function(key, value) { if (arguments.length > 1) { // > 1 args = this is a `set` return value; } else { // otherwise this is a `get` var _this = this; value = null; this.get(‘topic.course.lessons’). then(function(lessons) { // … Read more
You’ll want to use the Promise constructor: function writeToFile(filePath: string, arr: string[]): Promise<boolean> { return new Promise((resolve, reject) => { const file = fs.createWriteStream(filePath); for (const row of arr) { file.write(row + “\n”); } file.end(); file.on(“finish”, () => { resolve(true); }); // not sure why you want to pass a boolean file.on(“error”, reject); // don’t … Read more