This time I’ve
got an interesting batch of conference talks, as I listened to talks from recent
conferences, like ngConf and Uphill Conf. ngConf is the probably the biggest Angular
conference in the world and I would love to attend it someday! (Watching live
feeds from people on Twitter made me envy them so much…)
1. Conference talks
>> “Wrapping it up with decorators” by Nicole Oliver
Decorators
are probably the most underused TypeScript feature when developing Angular apps
(at least for me). They let you modify existing functionalities of class and
its members.
First time
I’ve heard of an idea of decorators was in Java (there called “annotations”). They
are part AOP (Aspect Oriented Programming) and allow you to extract repeatable functionality
and reuse it. It takes shape of a function of a certain type (different type
for class, field or method to decorate).
Nicole shows
us not only how to create and use basic decorator in TS. She also shows us how
they work internally and how to use basic concepts of meta-programming in JS for
our advantage (with PropertyDescriptor).
>> “Can you imagine a future without zones?” by Maxim Koretskyi
We happened
to talk about zones already and how crucial they are, especially in Angular. Maxim
shows us an example Angular app and how we can maneuver with its settings to
enable, disable and optimize zone usage and what are the consequences of those
actions. We also get to know how Angular itself takes advantage of Zone.js
library.
>> “CDK Is The Coolest Thing You Are Not Using” by Jeremy Elbourn
Here we
hear the news related to Angular Material and CDK changes (recent or near-future
ones). Angular Material is a library of the most often used UI components (like
navbars, cards, lists, drag and drop, etc.). On the other hand, CDK gives us,
developers, tools for creating components ourselves.
Jeremy shows
us the newest components in the Material family and how he and his team are working
towards further evolution of the projects.
>> “20 RxJS operators in 20 minutes by Mike Brocchi & John Niedzwiecki
Mike and
John present us with 20 common and uncommon RxJS operators. They do their speech
brilliantly with both humor and expertise (I don’t mind dad jokes at all, even while
not being one myself ๐). I wrote some of those operators down
in my own RxJS dictionary.
>> “RxJS Recipes” by Dominic Elm and Kwinten Pisman
This is a
wonderful talk about common RxJS patterns. With the sample app, Dominic and
Kwinten present us how to solve problems with “divide and conquer” approach and
making use of patterns and recipes.
Watching
this talk, in particular, made me very excited, as they opened my eyes on how
useful can RxJS actually be. Thanks to great talks like that, reactive
programming is starting to feel much more natural for me when developing web
apps. I wish there was a book/course on advanced RxJS patterns somewhere out
there.
Does anyone
know some?
2. JavaScript misc.
>> RxJS: Subscription and add()
This is one a very useful tip I found a while ago and it is worth sharing, as I see many
people are unaware of this. You can add multiple subscriptions to one
Subscription instance and then .unsubscribe() it whenever necessary to unsubscribe
from all of them at once.
I mention
it because I see a lot of people solving this problem by creating an array of Subscription
instances and looping over them and unsubscribing. I also see some people sharing
some npm libraries which solve this non-existing problem.
>> “Debugging RxJS” and rxjs-spy by Nicholas Jamieson
I found out
a nice way of getting valuable information on your Observable instances
currently running in your app. For that, use rxjs-spy npm package. With one
command in the browser’s console, you can extract the state of your observables,
how many subscribers it has, what is the value inside, etc.
I used and it
was incredibly helpful, as I found a couple of subscription leaks, totally
unaware of them before.
>> Typed reactive forms in Angular?
[GitHub issue] [@ng-stack/forms] [ngx-strongly-typed-forms]
One thing I
found awkward about reactive forms in Angular, that they are not as strongly
typed as I wish them to be.
There is already
a GitHub issue for that (linked above). For now, we can create our own type
aliases that suit our needs or use external solutions, like those above.
I saw that there
is an already rough discussion on that topic going on. People want (even
demand) new functionalities over and over. There is probably a lot going on in
the Angular team already, so please, be patient and understanding. Those folks are
doing a really good job.
>> Promise: then() + error callback vs catch()
Interesting
thread on using one of many Promises’ features. I was wondering what’s the
difference between using error callback in then() or just using catch().
TL;DR: Using
error callback might miss error that would occur in handler inside then(). So…
If we want to handle errors properly we should always use catch(), right? Yup,
JS is weird.
>> Does unresolved Promise cause memory leak?
Here is Stack
Overflow thread on that topic exactly. I was wondering what are the
consequences of not resolving a Promise.
One thing
is sure, if you create a Promise that never resolves/rejects, you create
forever-pending Promise instance. I think that one of the comments says it all:
@cdhowie: “There's
some truth in these comments and some that's misleading, so let me clarify: A
promise with handlers attached might be eligible for garbage
collection. A promise is kept alive (not GC-eligible) if any of
the following are true: (1) there is a reference to the promise object, (2)
there is a reference to the "deferred" state of the promise (the object/functions
you use to resolve/reject it). Outside of this, the promise is eligible for GC.
(If nobody has the promise and nobody can change its state, what is its purpose
anymore, anyway?”
3. Other
>> "Awesome" GitHub repository
This
repository is one of the best and the biggest learning resources you can find on
the Internet. It consists of many references to learning articles, tutorials,
courses, videos, etc. A great starting point if you want to level up as a
developer. I personally found many resources on the basics of functional
programming and Elm there.
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