you may seen often if watching Angular tutorial :D

Same. A terrific teacher ☘️

indeed he rise the bar

100%

Thanks. I appreciate that. That's really cool that you think it's good enough to do a video on. I'll definitely think about it.

Whoops, my bad.

Thanks!

Thanks!

Thanks for the feedback!

Oregon. Although this is Lacamas Park in Camas, WA.

The legendary Bill Joy once told me that the fundamental flaw of the "management" panacea of adding new programmers to a team that is behind schedule is that the rate of new code generation per developer expands linearly while the rate of new idea generation per developer expands exponentially. Since overall team productivity is the ratio of the former to the latter, team productivity asymptotically approaches zero as developers are added.

i really appreciate what you are saying, and I've put a ton of thought into this. My original idea for this channel was "compelling content, outside the paywall on KZfaq, for anyone". I've done some behind the paywall stuff and I don't like it. I think anyone should be able to teach themselves to code by using videos and do it for free. But the big publishers have an audience, and out of the box on KZfaq, I haven't had one. So I started doing almost exactly what I'd do for Packt or O'Reilly. Professional titles, business style thumbnails, etc. I didn't want to "sell out" to the KZfaq algorithm. And the result is that this channel has grown relatively slowly in comparison to my contemporaries. e.g. Florin Pop started YouTubing a year after me and has 5+X more subs. And we cover very similar topics. Problem is that my click thru rate (CTR) is low. I've got content people like to watch when they get to it, but they don't because either the thumbnail or the title isn't compelling. I've done a lot more on the thumbnails lately and it was improving, but not by much. This video however, with its clickbait title, has done 10X the views, 2X the view time, 3X the CTR and gotten me a bunch of new subs over last weeks release. Here is how I look at myself on the mirror on this; I'm NOT lying with this title. People are doing react hooks wrong _probably_ in that most of the folks I get comments from or interview don't know how to use dependency arrays. So, for those folks, they are using them wrong and this gives them an entry point into learning how to get more out of them and demystify them a little. And for folks already using them that way, then it's something they can point to and get some self-confidence. Anyway, unseen content helps nobody, is my long winded point. So it's either keep it free and give a little on my KZfaq "purity" or go behind the paywall and pick up the their audiences and but also play to their editors fiddle.

@@jherr Many thanks for taking the time to shed some light on this stuff. Hope I didn't come off too harsh. I understand you gotta do what you gotta do to make your channel flourish, and it couldn't be more well deserved!

@@thatboyneedstherapy Thanks man. And feel free to keep keepin' me honest. :)

"Imposter syndrome and gatekeeping are so common in our neck of the woods" - just admit it, you *were* using React hooks wrong before this video! ( /jk fergedsakes! )

Probably could have, yeah.

A Varmilo VA87M my daughter got me for my birthday.

If you give me a time reference I'll give you my reasoning about useMemo.

Fair. In this case I was looking for a term that captured the dependencies between the various pieces of state, derived state and effects.

I probably didn't have to. When it comes to useCallback expensive doesn't matter. That's just about useMemo and it's one of two reasons to use useMemo; maintaining referential identities and, as you point out, expensive synchronous computes.

@@jherr Got it! Thank you so much for the clear explanation.

OOTB feature. It's always been there.

react-use has some excellent hooks to track scrolling, and you can use the data from those as dependencies on useEffects to fetch more data. Same thing with a page index. If the page index is a dependency of the fetch useEffect then the fetch will fire every time the page changes to go and get the data for that page.

@@jherr Thanks for the advice, backend was also a challenge (in some way)

I've done a couple previously on React hook form. I might add it to a speed run though. It's a great library.

useEffect is "watch these values". useMemo is "compute this value from these values". and useCallback is the same thing but applied to functions. For custom hooks I would always use useMemo and useCallback because I don't know how the data and functions I return from the custom hook will be used. For component code, useCallback is optional, but I still recommend it if you are sending the callback to another component so that it retains referential integrity.

useCallback holds a function that needs to run when given dependency changes in this case, we wanted to fire it only with event.target and we didn't need useCallback's context to watch for updates from that dependent variable if we included "pokemon" variable somewhere in that "onSetSearch", it means we want useCallback to know about "pokemon" too i hope this makes sense ;)

@@jherr I think the conclusion need to be: do you want to make react to be Reactive? You need to use: useEffect, use Memo and use Callback :-)

Uncontrolled inputs are fine. Preferred in a lot of situations. Forms managers like react-hook-form primarily use uncontrolled inputs.

Yeah. That’s typescript. You have to define what will go into the array. If you start with an empty array there is no way for it to know what you will be putting into it and making sure you always put the right kind of stuff.

@@jherr Thanks for confirming Jack. I've not used or read Typescript as yet. Trying to focus (reduce my learning curve) on learning JavaScript, React & Next.

@@simonedwards7101 I'm in the same boat. After more than two years of pretty much full-time React and NodeJS coding, I'm still struggling with basic syntax and "shortcuts" (such as the gazillion varieties of expressing an arrow function). I fully intend to use Typescript when I feel more confident of my understanding of the underlying Javascript that it relies on.

I have much much much love for SolidJS. This video me gearing up to show how SolidJS gets reactive state very right.

@@jherr Awesome, looking forward to it!. I've been looking at it's docs last weekend and it feels really well thought out.

@@jujijiju6929 Not only well thought out but blazingly fast. I wrote a search page for my BCC videos in it and it's insanely fast.

You should never ever have an empty dependency array. And no, you should not disable the linter, it is almost always correct.

@@jherr Thanks Jack!

It's always in the description of the video.

Yes. Exactly.

They are derived values. So the component can get re-rendered as many times as we want, but the min/max won't get re-computed unless the underlying data changes.

@@jherr i think useMemo should be used when we really wanna pass the value to other component? Since using useMemo uses memory and too many useMemo usage will eventually result a bad performance caused by first read-time to decide whether value will be memoized or not. I've seen a lot of apps using too many useMemo and instead resulting a slower app. or perhaps jack do u have any idea when it's the best time to stop useMemo? rather than memoized everything?

@@dellryuzi I haven't seen useMemo slow down an app. Comparing two arrays of scalars is a quick operation, and nobody is suggesting an app with useEffects is slower, and the dependency logic is the same between useMemo, useEffect and useCallback. If you're calculating an object or an array you should use useMemo because those are references, and if you do pass them somewhere to another component, or use that reference in a dependency array, you'll want it to managed by useMemo. If you are creating a scalar from useMemo then it's really a question of how long the scalar takes to calculate. If it's a simple expression then you probably shouldn't use useMemo, if it's the result of some iteration or a reduce, then you should probably use useMemo, otherwise not.

Night Wolf [dark blue] with MonoLisa

@@jherr nice, thanks 🙏

The example is more about how to manage control flow. But in reality, yeah, it's a small dataset and in this case fetch is just going to returned the cached data anyway. I'd probably also add in some debounce tho. :)

Thanks for replying! That makes sense and I didn't know debounce was a thing tysm!

That would be Github Copilot. Don't believe the FUD, it's not going to take your job. But it is going to accelerate your coding like I've never seen before.

@@jherr I've signed for it couple weeks ago but i thought ur using something else haha. thanks for the quick response btw🙏

It manages referential identity, primarily. So if you are constructing arrays or objects, and those are passed to other components then, as of today, those will be referentially managed to not trigger downstream effects, memos, callbacks, or updates to memoized components.

@@jherr Well.. Please check what I expose in my comment :) Epecially this part: -> "In the future, React may choose to “forget” some previously memoized values and recalculate them on next render" . >>>IN FUTURE REACT MAY CHOOSE TO FORGET

@@erdemsoydan4117 First off they "may" do it, and they don't now. And then there is "choose", and I read that it that under some circumstances, most likely low memory, they may go into a mode where they will invalidate this simple first order cache. (BTW, it's important to understand that `useMemo` stores only the most recent value, not all possible outputs.) Because dependency arrays work on ===, and === works on value for strings, numbers and booleans, and references for objects, arrays, and functions, you have to have a mechanism to control references for complex object types for derived values, and those mechanisms are useCallback and useMemo. Without them you'd have to resort to pushing the derived data into mutable state, which is incorrectly modeling the relationship between mutable state, and data that we derive from that mutable state.

@@jherr Thanks for your precious time. I have been working on mid scale app and we are using Context API (yeah not redux :)) . That scale and and using context API made me have extreme attention on rerenders. So I have no problem about understanding them. I also use useMemo sometimes but whenever I use I was hesitating because of the remark about useMemo in official docs as I mentioned above. I have been waiting to ask about this to someone "a true expert" like you on this case. Thanks for your answer. (Also In your example, if I was working on it, I would use useCallback instead of where ever you used use Memo. e.g Count over threshold : {getCountOverThreshould()} . Is there any drawback about this? useCallback instead of useMemo?)

@@erdemsoydan4117 It's been a while since I've looked at the code in this video, but if the `countOverThreshold` is a simple value I don't really understand the value of creating an accessor for it. It's certainly less surprising from an API perspective to have it be a value, as opposed to an accessor that returns a value. Can you fill me in a little on your thinking and why you believe this approach is advantageous?

That's Github Copilot.

We are, and we like it. Haven't watched the finale though, so please no spoilers. 🤣

Heh -- I rely on the linter to tell me when I need useCallback. My perhaps naive understanding is that useCallback is the mechanism to break infinite loops in the rendering/useEffect code. As the linter explains, a function that is needed only by one specific useEffect hook can often be refactored into a local function within the hook -- eliminating the need for useCallback. Your mileage may vary. :)

That’s correct. If the reference doesn’t change then it won’t fire. But… you can depend on the deeply nested value.

@@jherr I have a useMemo that I use that depends on react query data..I change the object property deep inside the project on a post call api call success response… but my useMemo doesn’t rerun for the new values.. maybe i have to go deeper in the object for my useMemo dependency array?

@@Knowwhentobluff you should depend on the values you use in the memo, deeply nested or not.

@@jherr even if useMemo is like “omg this is an unnecessary dependency”

Diagram.io