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Send me replies with vanilla JavaScript code examples that trip you (or tripped you in the past). No judgement. I mean topics like variables, functions, closures, recursion, objects and stuff.
Lol I thought I’d get one or two replies, didn’t expect to wake up to this. Thanks!
Btw I don’t want to share it very loudly yet but this is research for justjavascript.com which you might be interested in
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Dan Abramov
@dan_abramov
When you have an imperative API, where to put configuration is a no-brainer. Just stuff it right into the call!

$(div).toggleClass('active').fadeIn(500);
When you move to a declarative API, many imperative callsites turn into one.

You used to call $(div).toggleClass('active') in ten places, but now you setActive(!active) instead, and have one place that says:

<div className={active ? 'active' : null} />

Cool.
This helps separate the intent (“I want to change whether it’s active”) from implementation details (“when it’s active, we want this particular UI output”). Yay for separation of concerns.
Read 10 tweets
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Dan Abramov
@dan_abramov
If you have a cache and feel like eviction criteria are ad-hoc and unclear, it can help to have an explicit object that represents the caching lifetime. As long as you hold onto that object, you can read from the cache. Losing the reference to it means eviction.
This has implications for data fetching. The classic fetch-on-render pattern (like fetch in componentDidMount or effect) with local state is relatively easy to do because it *does* tie data lifetime to a well-defined thing. React state! It lives while component is mounted.
One of the many problems with this data fetching approach is that the cache is too local. If two components use the same data, you have to fetch it twice. Or lift it up. Redux is an extreme version of that. By lifting a cache too high, it no longer has a well-defined lifetime!
Read 10 tweets
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Dan Abramov
@dan_abramov
We need to talk about benchmarks in the JavaScript community. A typical benchmark used to compare libraries is 95% the thing being tested, 5% app code. The app code is rarely more than a dozen of functions in a couple of files.
The actual apps many of us are writing are the direct opposite of that. There’s a shitload of app code (hopefully with code splitting!), and then there’s the 5% which is taken the library code.
Here’s a few obvious problems that come out of that:

- A huge 25% difference in performance might actually be more like 3% (oops)

- A fixed cost difference in 5ms looks a lot more impressive against 5ms of app code than against 500ms of app code (oh no)
Read 12 tweets

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every_jorendorff
@jorendorff
JavaScript WeakRefs and finalizers are on the way to becoming a standard. This is terrible, terrible news and if you use JS you should know some stuff. github.com/tc39/proposal-…
PART THE FIRST: WeakRefs are toxic
WeakRefs are like cigarettes. You might really want one, you might convince yourself you need one, but it’s never good. The proposal itself says things like “they are best avoided if possible”. Not making it up.
Read 49 tweets
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Adam
@adancabdulle
#LOL For the last 2 years, @TheVillaSomalia has been curtailing the political associations of its opponents in Mogadishu. Today, the federal member states are blocking the president from meeting with his supporters in the regions....as you sow, so shall you reap!
This is not happening in isolation. In January of this year, @TheVillaSomalia issued a Persona non grata to the UN Special Representative to Somalia. Within the same month, FGS foreign minister & others were issued a Persona non Grata.
@TheVillaSomalia’s unchecked illegal, unethical & toxic tactics are introducing a new culture of divisive brinkmanship in Somalia.
Read 5 tweets
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Paul McBride
@ThePaulMcBride
Thanks to @NikkitaFTW's hard work on Code Sandbox, I've had the chance to compare @sveltejs and @reactjs on a small app. Here are my thoughts as a React fanboy...
Firstly, bundle sizes were closer than I thought they would be, ~420KB for the React app and ~320KB for the Svelte app. I suspect most of the size comes from Tone.js though.
The reactive `$:` syntax of Svelte looks weird but is insanely powerful. You can have a code block run each time any of the dependencies change without having to figure out what those dependencies are.
Read 9 tweets
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Elizabeth Reiher
@tonomoshia
R3D001: Statrted @udacity Front End NanoDegree (FEND) yesterday. #100DaysOfCode #GrowWithGoogle #udacity
R3D002: Cruising through HTML and CSS, filling in gaps. #100DaysOfCode #GrowWithGoogle
R3D003: Re-doing Animal Trading Card (HTML/CSS) in @udacity Front End Nanodegree #100DaysofCode #GrowWithGoogle
Read 123 tweets
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Dmitrii
@dmitriid
Ejecting react-create-app shows just how horribly and hoplessly complicated #Javascript infrastructure has become
I mean, besides the sheer number of moving parts, a third of configuration is about fighting bugs and behaviour in another third
Literally half of the code is "why the EFF isn't this default behaviour?"
Read 34 tweets

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