promises-spec VS proposal-iterator-helpers

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.

Very much agreed. The amount of mileage we get from using Spread (literally the ...) alone has been amazing. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... Iteration helpers is shipping soon, that'll be a huge help (async iteration helpers will be delayed for a while). https://github.com/tc39/proposal-iterator-helpers .

In the olden days, I feel like the codebases I worked on needed to use .apply() multiple times a week, to figure out some creative way of invoking functions. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... That's all gone now; I'd take even odds that 50% of my team knows .call and .apply.

Chrome 117 is shipping Object.groupBy() and that's gonna be a huge help in eliminating a lot of the last places we end up using lodash. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

Once this https://github.com/tc39/proposal-iterator-helpers reaches browsers, I'm prob gonna be exclusively using Maps.

No, probably not. But with iterator helpers, you can do

> focus more on improving the terrible JS web API

That's W3C’s job, not ECMA’s.

> Where are all the containers?

?

> Sorted sets/maps?

Sets and Maps are sorted (by insertion order)

> Why can't I even map an iterator?

It's coming, but someone will likely be exhausted by that addition. https://github.com/tc39/proposal-iterator-helpers

Upcoming: https://github.com/tc39/proposal-iterator-helpers

Not Generators, but Iterators have a Stage 3 proposal with helpers like these.

I guess you are not the only one dealing with this. That’s why there is this proposal https://github.com/tc39/proposal-iterator-helpers So hopefully it will get easier soon. But in most cases you can simply wrap it in Array.from or you can also clone with the spread operator.

Let's assume Number.range(), iterator helpers and some isPrime() function. From that we could easily create the following: