promises-spec VS q

Today, I tried implementing Promises/A+ from scratch to test my coding skill. In the process, I’ve crafted this guide to share my insights and experiences with those who share a similar interest. Without further ado, let’s dive in.

That made me chuckle.

For those not familiar with the promise design controversy:

http://brianmckenna.org/blog/category_theory_promisesaplus

https://github.com/promises-aplus/constructor-spec/issues/24

https://github.com/promises-aplus/promises-spec/issues/94

If you really want to go down the rabbit hole on this one, start here

Advantage 1, nesting, is the most important here, and it's often the most-overlooked advantage. Overlooking nesting is how Promises in Javascript got to be fundamentally broken.

Have you read the infamous GitHub thread where people tried to fix this before it got finalized? It's quite a trip

1.) JS implementation of Promise is not a monad. See this StackOverflow answer or this GitHub discussion for more details

In this article, we will go over how to implement a basic version of a promise during a FAANG interview. The standard for promise implementation is called A+, but it includes a huge amount of details, making it almost impossible to implement all of them during a one-hour coding interview. Therefore, we will focus on implementing a basic variation that should be enough to show the interviewer your solving skills.

Hey, at least you weren't these guys: https://github.com/promises-aplus/promises-spec/issues/94

Total carnage

How can I achieve this in NodeJS. I wonder if Q Library can be utilized in this case

Prior to ES6, we used bluebird or Q. Now we have Promises natively:

JavaScript Promises were a nightmare to wrap my head around. Not the fancy async/await syntax we have now, but the early stuff like kriskowal’s q. Wasn’t really until Promise was native did I fully understand it. Someone told me “the .then function only runs if you call resolve() in the previous block”. I think that’s what made it click.

I have some code that returns a promise object, e.g. using Q library for NodeJS.

Before promises arrived natively in JS, there were(and still are) many separate independent promise implementations in the form of third-party libraries for example Q, RSVP, etc. Even jQuery has its own custom implementation that they call deferreds. The name and the implementation might differ from library to library but the intention is the same, making asynchronous code behave like synchronous code.

Promises are a popular way of getting rid of callback hell. Originally it was a type of construct introduced by JavaScript libraries like Q and when.js, but these types of libraries became popular enough that promises are now provided natively in ECMAScript 6.

Another great library is Q https://github.com/kriskowal/q. This library is exposes the concept of promises. A promise is basically an object that is returned from a method with the “promise” that it will eventually provide a return value. This ties is very neatly with the asynchronous nature of javascript and node.js.

q : This module is used for creating custom promises. Check it out here