Debouncing in Javascript | Flipkart UI Interview Question
Вставка
- Опубліковано 5 жов 2024
- Debouncing is not just an important interview question, but it is also very useful to improve the performance of large scale web applications. A question based on this concept of Debouncing was asked to me while I was giving an interview at Flipkart.
Topics covered in the video :
1. Real-life scenarios using Debouncing to improve performance
2. Flipkart Interview Experience - question-based on concept of Debouncing in JS
3. Step by step approach of writing debounce function in the interview - Polyfill for debounce function
4. Code for implementing our own debounce function
Link to code - codepen.io/aks...
If you get to learn something from this video then do give it a thumbs up and subscribe to this channel for regular awesome videos.
If you find my videos helpful,
then please support this channel by buying a coffee,
www.buymeacoff...
Cheers,
Akshay Saini
akshaysaini.in
Would love to Stay Connected with you ❤️
LinkedIn - / akshaymarch7
Instagram - / akshaymarch7
Twitter - / akshaymarch7
Facebook - / akshaymarch7
#Javascript #JavascriptInterviewQuestions #AkshaySaini
Hi Akshay,
Because of your true efforts to learn and let others learn, i today got selected in amazon. Thanks a lot 🙏
Hearty Congratulations, Vishal. Keep shining! 😇
@@akshaymarch7 thanku akshay. Looking forward for more of your videos. U can even make videos on react. Would be awesome
@Vishal it would be great of you could let us know what Amazon expects from a front end engineer in interviews
@@vishalbisht6871 Hello Vishal can you Please tell how you have prepared and how you got the chance for the interview.
@@shivrajnag12 probably by studying in iit
Very good explanation @Akshay. However there are few bugs and unused variables in the code.
1. You haven't used 'fn' param in debounce function, though you have passed the 'argument' - 'getData' from 20th line.
2. If you had used the 'fn' param in the setTimout function, you would have avoided the getData function in line no.15
3. If you had adjusted the 2nd point right, you wouldn't need to keep the reference of 'this' and 'arg' unnecessarily, It would have automatically keeps the outer function params value intact. ( That's what closure does).
@@SowmyaS-n6e
```
let counter = 0;
const getData = function() {
console.log("Fetching Data...", ++counter);
}
const debounce = function(fn, delay=300) {
let timer;
return function () {
const context = this;
const args = arguments;
clearTimeout(timer);
timer = setTimeout(() => {
fn.apply(context, args);
}, delay);
};
};
const fetchDebouncedData = debounce(getData, 500);
fetchDebouncedData();
```
Hello sir, where does arguments come from in the function?
Watching this at 2:03AM, feel like I learned something. Thanks Brother.
Watching this at 1:23 AM
Watching this at 1:03AM
Hey guys im just confused, like Does akshay messed something
1. fn.apply should be there instead of getData.apply inside setTimeout,
2. arg should be use if we are doing args = argument, like this fn.apply(context, args);
```javascript
function getData(){
console.log("hey");
}
const debounce = function(fn,d){
let timer;
return function(){
let context = this;
let args = arguments;
clearTimeout(timer);
timer = setTimeout(()=>{
fn.apply(context, args)
},d)
}
}
const delay = 250;
const betterFunction = debounce(getData, delay)
```
ikr markdown not gonna work in yt comment section
revising my concepts by watching the knowledge heavy js series in 2024, thanks aton Akshay, I learnt alot from your videos. ❤
Hi brother I am watching your videos for some time now and in intial period I thought this is going to be like other channels with few tutorials of this and then few tutorials of that but I was wrong this is purely javascript based 100% pure content, I am Software Engineer in test at EA sports I can say the info you provide is legit, I use javascript everyday and use atleast 60% to 70% concepts you covered. Keep on doing this, we need more content creators like you. Stay motivated stay hungry
Never knew the term but was searching for this functionality to implement in an ongoing project!
Learned and implemented a new concept (checked) :-P
Thanks for this amazing video!
Haha same. Saw this video 2 years ago when I was preparing for interview and now I'm using this for a project at work. There is another way to do it but I will use this so I can learn something cool :D
Hi Akshay, its really awesome work, you are doing. You explained debounce very nicely. Looks like, you missed to call fn() inside debounce method and instead you called the getData(). There is no impact on final output but since you are passing getData reference as first argument. So, it is better to call the fn(). Thanks Akshay keep doing this work. Friday night I started with one video of yours and i watched till 5 am morning. So, I have targeted to finish all your videos over the weekend. I feel like i am watching any online series. its to tempting and interesting. Thanks
I can see your comments regarding fn().
Nice example Akshay but there are two things that are missing in the explanation one is timer variable which holds the setTimeout as closure and clearing out the setTimeout callback going to the event queue for event loop using clearTimeout function.
If you are confused why timer variable need to defined outside of the anonymous function, that is closure !!!
Thank You. nice knowledge share.
Throttling is better way to handle than debouncing, as always last current data is sent after every throttle period. In any case, both approach still does not know how to clear last call already made to server (assumption is even server may take x time at server to service each call). It is important even server to drop obsolete call if respective next relevant request has come..
Hi Raja, Thanks for recognising the efforts.
However to add to your point, I won't agree that throttling is a better way than debouncing. They are altogether very different and we can't compare between them. But I've personally find myself stuck in many situations were debouncing helped me instead throttling. Thanks :)
Was not getting debounce for so long, but you made it clear so easily...! Thanks mann!!
Now if I have encountered with any question from interviewer and don't know it, I come here to understand it. thanks Akshay
Pls explain throttling and prototypes and prototypal inheritance and promises related interview questions. Also closures and currying and React js interview questions Akshay.
Videos for these topics are live now:
Throttling - ua-cam.com/video/81NGEXAaa3Y/v-deo.html
Prototype & Prototypal Inheritance - ua-cam.com/video/wstwjQ1yqWQ/v-deo.html
Great explanation. I am bit confused about the role of arguments and context here. How can we use them? Please explain.
Yesterday I couldn't answer this question in an interview and now m learning from your videos!
What company was that?
I am watching your video when my road is blocked from all side. This this the right place you will get right solution of your problem. Keep up the good work sir!
Great explanation, it was really clear! Just want to point out a little thing that you forget to use the parameter fn (the function passed to debounce function) instead of directly use getData function in the body. Keep up the good work sir!
that good to point out any mistake as i also think same but as no comment is there for this mistake , i just think i am thinking it in wrong way.
Found your channel very late. But I'm glad I found it now 👍
your explanation is superb thanks for making video on such topics
Hey aksay please make more videos on ecommerce design logic please
Hi Akshay,
Correct me if I am wrong.
In this case, there is no need to bind the getData function like getData.apply(context) where context is pointing to "this'".
debounce function is in the global scope. so "this" inside it is pointing to global i.e window object;
"this" keyword in the anonymous function that is inside the debounce function point to the input field.
And finally, since function inside the set timeout is an arrow function, "this" inside it will automatically take its reference from its enclosing scope that is an outer anonymous function.
So "this" inside arrow function point to input field.
But since getData() function called without "this" keyword so it automatically points to the global scope where getData() function is defined.
Now I can say I can implement debouncing anywhere needed😅. Thanks Akshay
Thankyou so much for sharing these importing concept with very ease, it helping me in my skills and also in my interview.
One of the best instructor . Thank you for your generosity.
Hi Saini, Lately I found your videos, Your videos helping a lot for me to understand the core concepts of Javascript. Thanka a lot.
Namaste Akshai, I think here storing context "this" is not necessary since "this" is by default window inside the setTimeout in a non-strict mode. It would be useful if we use functions as classes to store "this" context. Also, you need to define the context outside the return function, since "this" is a reference that is not present as a variable in a lexical scope so the closure formed cannot remember and "this" by default points to Window. PS: the word lexical scope learned from your youtube video series Namaste JavaScript.
Yes, this is my doubt. This is global so not lexical.
Best thing learnt today. Found your channel today itself after seeing your post on LinkedIn. Your videos are really helpful. Thank you Akshay. 😊👍
after watching this video 4 times now i understand this concept ... :) thnks for this ....
Awesome... Was working on a search bar yesterday only... and the app feezed... Thank you introducing this concept.
Thank you so much, Akshay. You really doing very helpful job, explains every with such simplicity that even complex concept doesn't seems complex any more.
You're most welcome! 🙏
I had used debouncing earlier but that was through lodash library ....Great Video :)
Yeah, it's best to use the loadash library if you're implementing debouncing in your webapp. But in interviews, it's frequently asked to write your own implementation of debounce function, just to check if the candidate understand what happens behind the scenes or not. 😊
@@akshaymarch7 Yeah I did implement first time in your video :P . Will definitely implement one in interviews if asked ;)
I added the code as a repo for those who would like to refer on Github. Here is the link : github.com/prateek951/js-interview-questions
Thanks Akshay :) . It's an awesome refresher.
@@TheNerdyDev Wow! that's awesome man. Thanks a lot for helping everyone. :)
I have nicely understood the concept of debouncing method except that `apply( )` and `context`. Can you please suggest any link for context and apply method ?.
Very nice explanation 👌✨🎉
*** DOUBT ***
1) Why did we use fn.apply( );
2) " context = this, " what will this refer
3) 'args = arguments' what are arguments ? is it a reserved keyword ?
1. So you can preserve the value of `this`.
2. The input element as it created the event.
3. Yes, it is. You can use it inside any function to get all the arguments in form of an array.
I just love your videos brother you put all all your efforts in the explanation....I have found very few tutors who go that deep into the concept...love your work..🎉
one more efficient way is to check for spaces and stop words, and also cache those requests (memoize) along with debounce so that the API request to the server can be minimized and better auto suggestion.
in modern scenerios, combination of debounce and throttling is used. and cache is always preferred.
Hi Akshay, thanks for better explanation. Please keep posting such type of new things that will help people's.
jab se maine Akshay bhaiya k namaste javascript video ko dekhna start kra exdm se love hone lga javascript mein.
Ab main kitne bhi hours javascript mein code kru mereko boring ni lgta.
Thankyou so much bhaiya for making these kinda videos.
very nice explanation agian :) 😅😅
Dude you are my fav person right now.. keep doing what you do man! Giving hope in these harsh times!
Hi Akshay,
You have explained dobouncing very well. Looking forward for more videos like this.
Released a related video today, this might help you - ua-cam.com/video/81NGEXAaa3Y/v-deo.html
Very nice 👍
recently i came across the videos of your channel and it has helped me to understand and getting mind set how to think of a solution for real project complex optimization. Keep publishing video with these simple easy to the point explanation.
thanks a lot. I just implement this concept in my project it makes a huge performance boost
please come up with the more useful and hard topic of Javascript. Thanks a lot for Debouncing. it helps me.
Bro. I not watched video and hearing audio only easy to understand that speaking. Smart learner to teaching easy way to know the concept... Smart move.. now I'm going to watch the video...🎉❤️
Was using this concept since long, but now I get to know about it. Thanks man. Awesome video. Awesome explanation.
Explained in such a simple way!
Hi Akshay,
I guess you did not use the "fn" param in return function.
e.g ->
const debounce = function (fn, d) {
let timer;
return function() {
let context = this,
args = arguments;
clearInterval(timer);
timer = setTimeout(() => {
fn.apply(context,arguments);
}, d);
}
}
this debounce also working same like the one which you showed in video but the difference is as follow->
fn.apply(context,arguments); => getData.apply(context,arguments);
i don't understand how timer, when passed as argmnet in clearInterval isn't throwing can't access error?? What about Temporal Dead Zone?
Hi Akshay,
I think you did a pretty well job but to make it simpler to understand you can also write it as:
// debounce method
const debounceRequests = (fn, delay) => {
let timer;
return function() {
// clearing timeout
if(timer) {
clearTimeout(timer);
}
// setting timeout
timer = setTimeout(fn, delay);
// no need to use apply method and creating context since already passing an function as callback
}
}
// normal function to fectch data on key press event
let counter = 0;
const fetchData = () => {
console.log(counter++ + ' fetching data.. ');
}
const makeDebounceReq = debounceRequests(fetchData, 300);
Let me know if you have any better solution.
Regards,
Amit Agrawal
Learned the concept. Thank u very much. Will use in my existing and future development.
question: why don't we just use debounce(getData, 300) IN the event callback? I tested this and works also. Why do we go the extra step of returning the function into another variable (betterFunction) and passing that as the event callback?
Hey dee. Which method did u call in html keyup?I also did try this. But won't work
@@alradiation5417
let debounce = function(originalFunction, delay){
let timer;
return function (){
clearTimeout(timer);
timer = setTimeout(() => {
originalFunction();
}, delay);
};
}
let fetchData = function(){
console.log("fetching data");
}
const INPUT = document.querySelector("input");
INPUT.addEventListener("keyup", debounce(fetchData, 300));
So how will you pass in parameters for this function, that's why we use apply method
Explanation is so good... Loved and well understood.. Thanks lot
Minor correction:
At line 11 (timestamp- 7:54), it should be fn() and not getData()
I really start loving you and your effort :) Thanks man for such an easy to understand tutorials on JavaScript
why the dislikes... someone not liking a good free content ?
0:00 Intro
1:14 Context/Recap
2:58 Code init
12:26 Code complete & test
13:40 Refactor & Conclusion
Hey Akshay
Thanks a lot for this video
Can you explain the lexical context for this video,
we have declared timer variable debounce function, it will return again a function which is a different context, but every time onkeyup method called the timer is declared again how does it holds previous timer object
Can you explain me ?
Wondering about the same thing.
See, the debounce function is called only once as soon as the page is loaded in browser and returns a new anonymous function and gets attached to the better function. so the timer variable here is lexical scoped inside the debounce function right?? so whenever onkeyup event is triggered the anonymous function is called (and not the debounce function).. and the anonymous function's setTimeout points to the same timer variable :)
Akshay you have done a great job.
I can understand it would take more time behind the camera for making understand well. So keep it up this good job and helping us
One suggestion sir make video description with explanation of denouncing as I was searching for same feature but couldn't get
Sir! Your videos are really unique and great. Please keep posting more awesome core stuff like these.
Amazing content Akshay
here's another noob question:
why do I need to return a function or do debouncing at all, when I can do this?
const onInput = (event) => {
if (timeOutId) {
clearTimeout(timeOutId);
}
timeOutId = setTimeout(() => {
fetchData(event.target.value);
}, 1000);
};
Yes 👍 optimized code.
Can you make a video on progressive image loading / lazy loading? How it is done effectively? I can find many implementations out there but confusing
ES6 version of this solution :
let counter = 0;
const fetchFunc = (e) => {
console.log("Fetching data...", counter++,e);
};
const debounce = (functionRef, timeInMS) => {
let timer;
return (e) => {
clearTimeout(timer);
timer = setTimeout(()=> functionRef(e), timeInMS);
};
};
const debounceFunc = debounce(fetchFunc, 300);
if i console.log(e) it is giving undefined
I am using the search based on API results without debounce method in my office project. Now I will replace my code with debounce method. :)
You explained it really well. Can you pls make some video or tutorial on vanilla js also.
Hi Akshay,
I have used takeLatest of redux saga so far to cancel the frequent API call. but it is limited to only when there is saga is going on the new task will be cancelled.
This method of debouncing is really useful
Thanks a lot Akshay for amazing explanation on debounce. Requesting you to make similar videos on subject and behavioursubject.
Very good video , helped to understand the concept clearly with a real-world example. But why to make things complicated with context, apply and arguments ? Cant the below code do the same purpose ?
const debounce = (fn, duration) => {
let timer;
return () => {
clearTimeout(timer);
timer = setTimeout( () => fetchData(), duration);
}
}
It will also have same effect! 👍
imagine you have some parameters in the handlerFunction.... how would you pass
Thanks for your video! love it. One typo: line#15 should be 'arg' instead of 'arguments'.
You are doing an awesome job akshay👍👍👍....I am using your videos as tutorials for preparing for interviews... the way you explain with examples and codes is really very helpful ... makes understanding the concept very easy... keep doing more such videos 👏👏👏
Thanks @Akshay Saini For Awesome Explaination
Within debounce method, the first argument is "fn", i believe in the function line no 15, instead of "getData", fn should be called
@Akshay Saini HI, this was amazing but can you tell me why "let context = this and args = arguments" line is written i mean what is use of it?
bhaiya every video is new eye opener in itself!
Really cool concept bruh. Will write a article and will post your video in that .
Yeah, Awesome. Totally Practice and application.
Good and simple one. Can you please do a video on how to avoid logging 2 service call in network tab of chrome for each service call made. Although only once service call actually made to the server.
Thank u sir 👊🏽 learnt a-lot from your content !!
Great lesson, but one thing - getData() can't use 'this' biding. I think it should be written as regular function
This is something new to me. Thanks for sharing. 🙂
Hi Akshay. It was a nice and crisp explanation of debouncing. Can u also make a video on throttling ?
Thanks Manish, I've noted and will come up with a video on throttling soon. 😊
Great informative video. Thanks
This was awesome! Now i want to implement custom search bar in React with a database. 😂
Thanks , I learned something new today.
very nice way you explained
simple way, deserved subscribe bro
Perfectly clear and concise. Thank you!
Awesome explanation! Can you please make a video on arrow functions and this keyword in js.
+1
Please keep making such enterprise level question videos along with solutions...u r doing great bro keep it up
Great tutorial Akshay.
Thanks for explaining and teaching the concept of debouncing in such an easy way.
GBY
Excellent! Using straight away in my application. What is filter you applied by the way to just filter autosuggest apis? It is great way to demo to the team.
Hi Akshay I am confused in one scenario. What is the difference bw the two in debouncing.
1) const betterSearch = function () {
debounce(search, 3000)();
}
2) const betterSearch = debounce(search, 3000);
The first does'nt work while the second works.
I checked both , both of them worked fine in my script
@@Moonwalkerrabhi have you added log statements to see if it was denouncing or not?
@@sarthakbhatia7639 Yes i did
We want video on throttling!
Thanks Akshay😊 it was a nice demonstration on an important topic. Looking forward for more of these type of videos.
P.s. You're awesome!
Abracadabra, here it is - ua-cam.com/video/81NGEXAaa3Y/v-deo.html
The content and explanation is good. Thanks for sharing the valuable information with lots of effort.
I found one issue in the your code due to that it should not work as debounce. You must declare "timer" at Global Scope not in doSomeMagic function scope. Right now it is creating new variable for every call. So, clearTimeOut fucntion would not have anything to clear. That means every timeout function would call.
eagerly waiting for closures and design patterns
God level clarity bro
Hello Akshay! Thanks a lot for your tutorials! They are amazing!
I have a question: Why do you and many sites on the internet show this example using ARGS and THIS, if you could simplify and make something like this that is much easier and straightforward to understand. This is tested and working! What am I missing here?
import * as React from 'react';
export default function App() {
function debounce(cbFunc, timeout = 300){
let timer;
return () => {
clearTimeout(timer);
timer = setTimeout(() => {
cbFunc()
}, timeout);
};
}
function fetchDataHandler(){
console.log('Fetching data from API');
}
const fetchData = debounce(() => fetchDataHandler(), 500);
return (
Search API
);
}
Hi Akshay, how debouncing is different from throttling? In throttling video you showed similar example for delaying the event using flag instead of timer.
In case if anyone looking for shorter version:
const debounce = (fn, wait) => {
let timeout;
return (...args) => {
clearTimeout(timeout);
timeout = setTimeout(fn, wait, ...args);
}
}
Nice one 👍
Hello Akshay, I liked how you asked the questions to reach to the solution..
can you please make some videos on how to approach towards a solution of a particular problem..
is there any process that you follow to solve complex scenarios..?
Hi Akshay,
First of all thankyou so much for sharing this beautiful concepts with us. I am really liking your all sessions😇. I just have a request , could you please explain about indexdb also
Thank you so much for this clear explanation. Thanks a lot.
Excellent explanation ..Thanks a lot
Thanks Akshay for making these videos.