Learn useRef in 11 Minutes
HTML-код
- Опубликовано: 4 янв 2025
- 🚨 IMPORTANT:
Full React Course: courses.webdev...
In this video I cover everything you need to know about the useRef hook. I go over all the main use cases for useRef as well as many common mistakes that developers make. This is part of a series of React videos where I cover all the important hooks in React.
📚 Materials/References:
useRef Blog Article: blog.webdevsim...
React Hooks Playlist: • React Hooks
🧠 Concepts Covered:
How to use hooks in React
How to store values between renders in React function components
How to use the useRef hook
🌎 Find Me Here:
My Blog: blog.webdevsim...
My Courses: courses.webdev...
Patreon: / webdevsimplified
Twitter: / devsimplified
Discord: / discord
GitHub: github.com/Web...
CodePen: codepen.io/Web...
#ReactJs #WDS #useRef
If anyone is still confused about the last example. Here is a simple explanation.
Just keep three things in mind.
1. useState() causes re-render.
2. useRef() DOESN'T cause re-render.
3. useEffect() runs AFTER render.
So the flow goes like this. name = "" prevName = ""
-> Lets say you put "A" in the text field , so setName() runs. Changes the value of name = "A" to this. Component renders.
-> Then useEffect is run where you set prevName to name. prevName is the same as name which is "A" but here comes the 2nd point i wrote. useRef() DOESN'T cause re-render.
-> So when you changed the name , component got rendered and useEffect caused the prevName to change. But the thing is that component has already been rendered with whatever value prevName HAD before setName() got called.
prevName is not STORING the previous value of name. It is only DISPLAYING the previous value of name.
Hope this helps.
Great Explanation 🤩
Is it safe to say that useEffect() uses the data from the previous render ??? and I understand we store it in a useRef() since it wont cause a rerender .... but what's the difference using a useRef() variable oppose to just updating a normal variable ... NEED HELP
@@user-zv6bv7eu8k Because if you change the declaration to be const prevName = , then prevName would be set to at the start of every re-render whereas const prevName = useRef() will set prevName to only on the first render. Subsequent renders will set prevName to the whatever the last assigned value was. Hope that helps!
thanks!
@@waynerandom11 Thanks for your great explanation!
I rarely use to comment on videos, but i think this video deserves an specific acknowledgment. It was an excellent explanation about useRef, and the way that you showed the difference between it and states is super important. I hope you keep helping us, amateur web developers, to keep improving. Hope you have a lovely weekend ❤
Thank you so much!
i agree. i would like to see more advanced stuff, because he explains things very well and clearly.
I might purchase your course despite already knowing react. great vids bro.
Thank you!
@@WebDevSimplified c b0
@@WebDevSimplifiedy yyyyyyyy
@@WebDevSimplified hhyyt5
Lol
for people confused of what is happening in the last use case of useref, useEffect by definition runs after the things gets rendered.
so he is basically printing the value of the useState before assigning it in the useEffect
Thanks for clearing that, have been looking through the comments to figure that out.😃
And after the render, useEffect gets called and changes the value of prevName.current to current name,
And even though the prevName.current currently holds the current name after useEffect, it won't trigger a re-render
And that's why the prevName.current used in the return statement prints the previousName right?
Thank you for that Elie, I spent a decent time trying to understand what is going on and why is behaving that way.
Thanks a lot
thank you very much!!!
I hope this comment will help someone who can't get a grip on it like I couldn't for some time... When you are trying to understand logic of these processes explained in the video, just keep in mind one important thing - useEffect() only runs AFTER your component is rendered. Like in the last example where we trying to get previous value of our name, I would say that prevValue.current is not actually storing the value of our previous name, it displays it as component renders - then useEffect runs, prevValue.current now storing value of current name, but because useRef doesn't make component to re-render, it "keeps that in mind", but doesn't display it till the next time component is rendered.
Oh gosh.. I was hoping I'll put it simple. I hope it makes sense. It took me while to figure out logic and I feel need to share it with people.
Thanx dude
I was struggling to understand this too. Thanks for clarifying what's happening!
Thank you!🎉
thanks
Thank you, I was specifically looking for this in the comments
Im using most of things you teach on daily basis but I am still watching your videos and in many cases Im finding gems that I never even thought about. Good job mate, keep doing it, its good content.
Hey Kyle, I'm watching some paid React course, but when something is unclear, I open RUclips and specifically look for your videos - I find them super useful, you can explain difficult concepts in a clear and relaxed way. I can see how every aspect of your videos (intro, speech, explanation, examples) are thoroughly thought out. Thx a lot for all of your effort!
Finally understood Refs properly.. You are a saviour❤️
after searching for about 5 hours this video finally answered all my questions. I can't thank you enough buddy. I wish you the best of bests.
not gonna lie, i went through the useRef from one of the react books today, and i didnt understand what it was, this video somewhat made it brighter for me, but not entirely. Gotta rewatch it in the morning! Keep it up
Man you're just so much the best React teacher out there. Perfectly structured, bite-sized lessons. 💪
I struggled a little bit trying to understand Ref in React and I constantly found a bunch of explanations with examples but no other like this video. It made me understand everything. Thank you so much Kyle, shout out to you for explaining Ref very simple and concise.
I really like the calm voice without super hyped energy,coz that's what i need for an educational video
Best 10 minutes I've spent today.
Little shortcut. Instead of doing const something = useRef(), you can use object destructoring and set it to const {current: something} = useRef(). This allows you to access your ref without needing .current.
doesn't work, because you have to set ref={something} later on
What I truly love about your videos are: They are really crisp and cover the crux of the topic magically in a very small amount of time! That takes great skill, keep it up!
I was googling for the actual use case of useRef and after long time i got satisfied watching your video ... You told exactly what i wanted to know.... A lot of tutorial had the same caption but not worth satisfying.
And the most appreciable is that you only took few minutes..
Every time I need to learn something new about JavaScript, I look for your videos. You explain everything so clear it couldn't be better
After watching the video I accidentally closed the tab. Now I am back, just give this video a like because your tutorials are really helpful.
bro i have been following your tutorial and none of them have failed to amaze me, your explaination is so onpoint and simple.
I honestly never thought of using useRef for anything other than DOM elements.
This is brilliant.
YOU ARE A LIFESAVER!!!! Been searching for how to reference a DOM node in React and here you are showing me what I've been looking for the WHOLE DAMN DAY. THNAK YOU!!!!!!!! AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
That was super useful bro. I always felt this concept was too complex and always avoided it. Now, I have a decent clartity within 10 mins. Thanks a lot
Just for my reference 9:07 .
Q) Why is prevName not same as name, as due to state change the render has happened and after the render has happened, the useEffect has called, hence prevName should be same as name (updated)?
Ans -
> the state is set asynchronously.
> the callback function in useEffect is executed synchronously.
I believe this happens -
As the state is set asynchronously, the rendering happens first and then the state value changes.
Within that time, as rendering has alredy been done, the useEffect is executed and the old value of name is declared to prevName.
Till now, the asynchronous state is completed and the name is got the new value.
But why use useRef when you can store the previous name value in a simple let variable?
@@tinujos8306 Those variable values will be reset after every re-render, and you will lose the value stored
I don't think it happens this way. Instead I believe it works like this
-Initially both state and ref are ''
-User types 'a'
-State change (synchronous) state = 'a' , ref = ''
-Re-render as state is changed
-All the UI is painted with the current state and ref value.
-Use effect is called since the component is mounted after re-rendering
-Current state value is assigned to the ref. (now ref = 'a')
-UI remains same (as change in ref doesn't cause any re-render)
-User types 'b' next to 'a'
-State change (synchronous) state = 'ab' , ref = 'a'
-Re-render as state is changed
-All the UI is painted with the current state('ab') and ref value('a').
Correct me If I am wrong.
I don't get time to learn by myself because of busy work schedule but through your quick and easy videos like this one I am able to....thanks! Keep up the good work!
Thank you so much bro, I used to be confused about refs most times even the react docs didn't make it as clear as this video. Thanks a lot
GOD BLESS YOU! I have a React interview tomorrow and feel very confident after watching your useMemo, useCallback and useRef videos!
I never comment on videos but this explanation was so spot on - it helped me so much converting a tutorial that was using dom selectors into react-syntax. So thanks a lot :)))
Your content really breaks these down in a useful way. Thanks so much, youve saved me a lot of time.
I think you have the best videos for react hooks on RUclips
Mate I watched so many videos and read so many articles, but I never saw anything like yours! Short and very well explained. That's what I needed! Thanks!!!
So happy to see this Channel almost reaching 1MI subscribers.
thank you so much. i spend two hours read the doc and it still confuse me, but with your explanation, it makes me understand the way to use this hooks. 😲😲
I'm pulling an all-nighter and i got my final exam on React in a couple of hours. Thanks for the video, so greatly explained
legendary channel, the gift that keeps on giving
Really had a great experience of knowing all the react hooks use cases. You did a very good job. Kudos, man!!!
The quality of your presentation is appreciated.
Thank you for the videos.
May Allah reward you for your efforts.
As with useMemo I thank you for thining down the difficult concepts of React. Greate examples! I can't wait to see some more hooks simplified.
Very high quality content.After watching many useRef videos ,i only understood from your video.
I love you, Kyle! You’ve made my React Day with this video. 🙏🏼 thank you!
Wow! what a straightforwad amazing explanation to useRef. I was tired understanding it from lot of videos and docuementation, but understood only because of you. thank you sir
For the first example of not causing infinite loops we can add the name dependencies in the useEffect too.
No,.. it will have a bug. Initially it will re-render once as it have changed the counter variable which is a state which over mutation cause a re-render. So an empty input have a count of 1 but we need a count of 0. This is where ref are used which dont cause re-rendering
That's what I thought
I somehow stumbled upon this video... Amazing Content.!! just wow!!. If you wanna learn refs then this is the ultimate source.
The. Best. Explanation. Of. useRef. On. The. Internet!
You solved the problem for which I sat for hours. Thank you very much.
These vids are gold!!! thank you for helping this aspiring dev understand things that some seem to just gloss over or explain horribly.
Thank you, you always give new knowledge. In 10 minutes you clear the concepts of 1 hour. Thank you so much for saving us a lot of time.
By far the best explanation of the useRefs hook I've seen. Well done.
Dude you explain such topics so good with easy examples and simple usecase that before even going anywhere else to understand some concept i made it a habit to go through your videos first. Thanks for uploading
perfect explanation, so i dont need any more videos about topic. Its high level, thank you Kyle ;)
your content is fabulous and most useful for working professionals
Man!! this is the most informative and well explained.
Thank you for the thorough explanation.
I have a question that is slightly unrelated to this lesson. At the 08:49 mark, how were you able to access the previous state of the name variable? Shouldn't the name variable have been updated till then?
I tried figuring this out myself, so I also put a console.log in there. However, the console log was showing the updated state variable, while prevName.current still contained the old state.
This is a bit confusing, so I would appreciate it if anyone could help or point me towards a resource that could explain this. Thank you.
useEffect is called after the render, so it renders the previous name and only after it happens it gets the value of the current name
> the state is set asynchronously.
> the callback function in useEffect is executed synchronously.
I believe this happens -
As the state is set asynchronously, the rendering happens first and then the state value changes.
Within that time, as rendering has alredy been done, the useEffect is executed and the old value of name is declared to prevName.
Till now, the asynchronous state is completed and the name is got the new value.
@@siddharthmagadum16 have you done a setstate , then a {state} below it..
@@siddharthmagadum16 If the state is set asynchronously, the rendering happens first and then the state value changes. Then how does when you print the state value it has the latest value?
execute the same code, and console log the value of prevName.current you'll figure it out yourself
It's always great to watch your video, Even if I know some topic and watch your videos, there is always something new that I get to know.
Keep doing the good work brother.
After watching this I used it in one of our Video player component and its just awesome. Thanks a lot for this video
I had a situation where I had to read qr codes, but the qr code component triggered and event multiple times when the camera was reading the qr code because of motion and low delay tim. I couldn't increase the delay time, because it would take too long to scan many qr codes and useRef hook helped me to solve my issue. Thanks Kyle for the great video.
Great stuff, sir. Never thought about Ref that way.
This guy deserves a like. Impressive mate. Thank you.
2:40 Giving the useEffect a dependency array with "name" in it will lead to the desired output without unnecessary rerenders. So this specific example is indeed possible with useState...
it is really surprising how good you are at explanations
Clear cut explanation ... Thanks kyle.. You are amazing person.
this is a good explanation but it is important to understand that the same can be achieved at 2:40 by coding:
useEffect(()=>{
setCount(prevCount=> prevCount + 1)
}, [name])
the second parameter to the useEffect hook tells the function to only update when the state changes for the variable in square brackets. In the case, the variable is "name" and so the count would only update for every keystroke in the input box (which has a value based on the state of "name").
I've noticed the same fact and started to read the comments if anybody had noticed it too. So the first use case is not so useful. We can achieve the same result with adding [name] in the second parameter.
Web Dev Simplified is so awesome - I agree -one must show gratitude - great work!
Best explanation for useRef. Keep the goo work brother !
Wow, thanks man, I'm going to re-watch this playlist every week or so for some time.
Straight forward, Perfectly explained with no bs, thanks a lot!
this playlist is very helpful: clearly explained, yet complete and concise. thanks.
As always liking the video before actually watching it because i know the explanation is going to be amazing anyway! thanks Bro!!
Awesome explanation dude, I hardly comment on tech tuts, you are just so eloquent and precise. Keep up the good work!
thank you! think this hook really shed light on my mini project. I can save the previous dom state and render it back on the page now
Clear comparison with useState and nice explanation of rendering lifecycle. Thank you!
Finally an amazing explainer on useRef. Thanks!
Thank you for the concise and easy to understand explainer. Love this and appreciate your work.
this video is so useful , now i know how to use useRef and useState , thanks
thanks i look forward to my project finishing and being able to say your videos were abig part of it
Magnificent explanation. Thank you!
this video just saved my weekend
No words, Just Thank you brother
Massive respect to you thanks for these hooks tutorials. I am hooked no pun intended. Thank you.
I finally understand "useRef" thank u 😍😍✌️✌️
Great video. Your videos make the topics so easy to understand, thanks for that. I know enough react to get myself into trouble so looking to purchase your course to get some extra depth on the topics.
Honestly this is better than college. I would even say this is better than a bootcamp too.
I was wondering about how to grab elements in react and this golden video popped up so thank you so much
Another great videos that I missed. Thank you !
Excellent tutorial on refs! Just what I needed.
Crystal clear. Good job.
Your videos are always such great content and really like how you make it concise. Awesome job man!
You really simplified my life. Thank you!
Most Clear 🔍 explanation on the web 🕸
Thanks very much for your videos. all the hooks you explained really makes sense to me now so thanks Mann
Your explanations are really great!
Best useRef's tuto ever
I definitely have to comment bec this video is amazing and the explanation is very concise but clear as well. Thanks bro!
You blow my mind best video ever! keep the great job
Beautifully explained!!
Thank you for this beautiful explanation.
Wow I think useRef finally clicked for me thanks to this video! Thanks a lot!
Amaaaazing explanation !
Excellent series of videos..bravo!
Kyle seriously knows what he is talking about !!!!!!!!!!!!!!!!!