promises-spec VS proposal-array-grouping

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

Global iterator type is coming: https://github.com/tc39/proposal-iterator-helpers

But a method named `groupBy` on iterators traditionally means a different thing: https://github.com/tc39/proposal-array-grouping/issues/51#is...

Global iterable type it's too late for, since there's many extant iterables in the language and on the web which don't have it in their prototype chain and can't reasonably be changed.

Array grouping to combine like data into groups using Object.groupBy() and Map.groupBy().

Array Grouping: A proposal to make grouping of array items easier.

They are coming out with array.group() soon, which is supposed to also fulfil the use-case of partitioning :) - https://github.com/tc39/proposal-array-grouping.

https://github.com/tc39/proposal-array-grouping for those curious

I'm also looking forward to map.emplace() and arr.group() and iterator helpers.

At the end of the day, it comes down to whether browser vendors are willing to ship the feature even though it breaks said websites, and they do have visitor data to back those decisions. If the rule was "never break any website ever", you'd be able to block proposals you don't personally like by crafting a website that "gets broken" by that proposal.

At least in the array grouping proposal, they did evaluate amount and popularity of possibly breaking sites, before eventually renaming the method from .groupBy to .group

https://github.com/tc39/proposal-array-grouping/issues/37

The proposal is described here.

Remarkably, this is now a TC39 proposal.

Proposal, Polyfill