Javascript Interview Questions ( Currying ) - Output based Questions, Partial Application and more

#JavascriptInterview #Javascript #FrontendInterview
Javascript Interview Questions on Currying will be discussed in this video including topics like Infinite currying, curry() implementation, Partial Application, Output based Questions etc.
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00:00 Intro
00:15 What is Curring in Javascript?
00:53 Example of Currying
03:04 Why Currying?
03:37 Ques 1 - Implement sum(2)(6)(1)
06:22 Ques 2 - Reusing Variable for logic
09:29 Ques 3 - Infinite Currying
13:47 Ques 4 - Currying vs Partial Application
15:57 Ques 5 - Manipulating DOM
18:22 Ques 6 - curry() implementation
24:22 Read the blog for this video
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Special Thanks to our members -
Srinivas Ayyagari

[@AmanSingh-qr3ld]

You are putting so much effort to make such topics easy for us. Thanks for putting content like this. We really appreciate it.

[@RoadsideCoder]

❤️❤️ Thank you so much, greatful

[@RoadsideCoder]

Correction for the last question - At 22:15 args.length is 1, which of course it is, then I said length of function is 4, and highlighted the four curried functions at line number 22. Which is kind of not the case here, Here, func is that sum function I passed as prameter to original curry function and func.length would be length or number of parameters that func (sum function) expects. Which in this case sum function expects four formal parameters which are: a, b, c, d. So four comes from here, not from the curried functions in line 22. Sorry for the explanation gap.

[@adityanarayangantayat7133]

Exactly what I was going to comment and ask! Glad to find your comment 😅

[@adimaralimuddin96]

it was the length of the first argument as callback function on the first call. if the arg.length == curryArg.length ? then only call the callback function.. this one is actually very usefull.

[@amansaxena4446]

you should also explain this The length data property of a Function instance indicates the number of parameters expected by the function. for some folks it could be possible they couldnt understand how func.length is coming

[@abhirocks723]

yes... by the way thank you for explaining

[@rajkishorshaw2379]

Currying is a function that takes one argument at a time and returns a new function expecting the next argument. It is a conversion of function from callable as f(a,b) to f(a)(b).

[@woongda]

this is one of the coolest thing I learn !! I have all those chained http post calls, now I can do post(data1)(data2)(data3)((res) => { something}) without using promise and async/await and at the same time, no callback hell. I can throw error and use try/catch like async/await does.

[@A1996ARP2075]

Great next make on OOPS concept and prototype related

[@pushpabhandari619]

Thank you sir, your video's is really helpful please continue this interview series

[@RoadsideCoder]

Yes, More on the way!

[@arjobansingh1940]

Great video, but i guess it was slightly confusing when you said, func.length. At 22:15 you said args.length is 1, which of course it is, then you said length of function is 4, and highlighted the four curried functions at line number 22. Which is kind of not the case here, Actually here func is that sum function you passed as prameter to original curry function and func.length would be length or number of parameters that func (sum function) expects. Which in this case sum function expects four formal parameters which are: a, b, c, d. So four comes from here, not from the curried functions in line 22. As according to MDN, length is a property of a function object, and indicates how many arguments the function expects, i.e. the number of formal parameters. This number excludes the rest parameter and only includes parameters before the first one with a default value. Nonetheless great video!

[@RoadsideCoder]

Yes, my bad.. That was a little gap in my explanation, I'll add a pinned comment for correcting this part.

[@arjobansingh1940]

@@RoadsideCoder Cool!

[@chaitanyayash2958]

Brother, you are a gem. Thank you so much.

[@karthikk1098]

Thank you so much for educating and your videos were super mind game. I know you are intended to communicate in simple English and react language. Since I am a beginner in JS, just excited to share this the one n only question I solved better. const arithOp = { add: "+", subtract: "-", divide:"/", multiply:"*" } function one(type){ return function(lhs){ return function(rhs){ const resultString = `lhs ${arithOp[type]} rhs`; console.log(eval(resultString)); } } } one("add")(3)(3);

[@RoadsideCoder]

Awesome! Thanks for adding this approach here

[@RahulKumar-ew1qw]

Now , watching this type of video, lets hit the interview.. You are best of best .. ,🔥

[@RoadsideCoder]

All the best 😎🔥

[@fishamit]

i believe that your example for the "curry" function allows for passing multiple arguments in each subsequent invocation of a curried function. Isn't it more accurate to allow only one argument in each curried call? by removing the rest and spread operators on "next", on lines 11 + 12. 24:16

[@dailyPractice1]

The best thing about this series is that "You are covering questions topic wise in each separate video", So we can say we covered few question on this or that topic.

[@RoadsideCoder]

Glad it helped you!

[@kartikkaushik4743]

Nice effort earlier I though it used to be a cuury made inside the kitchen only but in js how to used with the function its great ,brother you are great

[@hemantpratapsingh236]

This is gold ... 👍👍 Such a quality content . .. keep going brother...

[@RoadsideCoder]

🙏🙏

[@MrCoder-u9y]

Deserve a million subscribe

[@RoadsideCoder]

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[@ramuramu8910]

Thanks for u r video with clear explanation.

[@rahularora9153]

Great Work bro, keep it up

[@RoadsideCoder]

Thanks 🔥

[@gkinfos]

in question 5- Manipulating Dom we can get the ref of element in one variable and then keep on updating the content, so why curring adding more sense here?

[@pravinjohannes7699]

Thank you so much sir, it is very much helpful and all your videos have helped to understand the javascript very well especially all your interview videos sir, thank you so much sir

[@achyutkumarsingh7308]

Thanks for teaching a new concept

[@Jatindamariya]

Isnt question 5 (dom manipulation) here an example of using closures instead of currying? How does currying link to this question?

[@ankushladani496]

Great Quality Content....

[@AbhinashKumar-ql3tn]

impressive teaching methodology..

[@journeycalculated]

in my first call the Hr asked me waht web application do you use....i was noy aware what web applications are...? could you explain me

[@dev-suresh]

Super useful video. Thanks

[@engsmyle]

Thanks you for explaining it very well, I really understand it now 😅...

[@Karansingh_78]

sir i have a doubt in console.log(add(2)(3)(4)); when remove the last parenthesis it showing output as function [anonymous] , sir what will be reason?

[@BalajiAade-bm7go]

Bhaiya please reply in timestamp 15:58 actually I think the example you provide is actually behave like a closure not currying tell me if i am wrong

[@siddesh1210]

Interview has asked me so its become more difficult to write function if we use currying so why we are using it like : function add(a,b,c){ return a+b+c; } And same if we do currying it will take 2 internal function and than it will return us value. So bhaiya how should we answer this questions??

[@merakshay7623]

Hey piyush there is catch in function add(a){ return function(b){ if(b) return add(a+b) return a; } } example console.log(add(10)(0)()); if b = 0 then it does not return any function so its throw an error called TypeError: add(...)(...) is not a function here is a proper solution function add(a){ return function(b){ if(b !== undefined) return add(a+b) return a; } } thank you _/\_

[@MrCoder-u9y]

Great buddy

[@merakshay7623]

@@MrCoder-u9y thanks

[@TanmayKamath]

This time in Cars24 i was asked this question. You need to curry add if n number of arguments are placed in any manner after the function: sum(1)(2)()()()(3)

[@SIVAREDDY-e4l]

Only if the last argument is empty we can go for Infinite currying as the tutorial explained if the middle argument is empty it stops there itself and gives result. Anyway what was the answer you gave and how can we solve this problem?

[@TanmayKamath]

@@SIVAREDDY-e4l Yes using recursion, you have to check whether the arguments is equal to the function length.

[@shubamdadhwal3497]

Loved the video bro, although i think there is no need to do: 1. the rest and spread of next arguement 2. greater condition check i.e. (args.length >= func.length) OR correct me, if i m wrong somewhere function curry(func) { return function curriedFunc(...args) { if (func.length === args.length) { return func(...args); } else { return function (next){ return curriedFunc(...args, next); } } } }; Also for those who don't know - function.length -> returns the EXPECTED number of arguments a function is expecting excluding the default and rest parameter arguments.length -> returns the ACTUAL number of arguments passed to a function

[@praveengautam4689]

thanku for function.length explaination

[@debabratamukherjee9577]

Good Point 👍👍 But if i do not spread the next argument, the following function will not work --> curriedSum(1)(2,3); Hope you understand.

[@rahul.sarkar]

Please make a video on throttling and debouncing in JavaScript 🥺🙏

[@RoadsideCoder]

Yes that's in the way!

[@raammeena6650]

Really appriciate you content

[@master_coder8628]

Love your videos. 💙 Please bring fast too

[@RoadsideCoder]

Thank you!

[@Lavith_kuttu]

When the interviewer asked us to write a function for multipler6 (if I have given 3 it should return 18, if 6 then 36 ) this is called partial application. const mul = (a=6) => { return (b) => { return a * b; }; }; const mul6 = mul(); console.log(mul6(3)); console.log(mul6(13)); console.log(mul6(9));

[@anubhavmahajan230]

The last question was epic 🤟

[@gagansuneja7029]

My answer for currying function sum(args){ if(args == undefined) { let currentSum = sum.currentSum; sum.currentSum = 0; return currentSum; } sum.currentSum = (sum.currentSum || 0) + args; return sum; }

[@atharshakeel7277]

Great video and very well explained

[@RoadsideCoder]

Thanks ❤️

[@akshitatyagi5234]

So we will need to pass () as blank to stop the recursion in 13:31 otherwise the output is always a function . Is there any way we can do this without adding empty () in the end??

[@dkatorzaify]

Hi, you don't need to pass () as blank. What will stop the recursion is the "if" statement once it will be true, meaning once the number of args will match the number of functions.

[@akshitatyagi5234]

@@dkatorzaify If u will quickly run this in browser console, you can see it is always returning a function. Logic seems okay but its not working, without the ()

[@dkatorzaify]

@@akshitatyagi5234 This is strange... I copied this to the console and it does work. function curry(func) { return function curriedFunc(...args) { if(args.length >= func.length) { return func(...args) } else { return function(...next) { return curriedFunc(...args,...next); } } } } const sum = (a,b,c,d) => a+b+c+d const totalSum = curry(sum) console.log(totalSum(1)(2)(3)(4))

[@akshitatyagi5234]

@@dkatorzaify I am talking about the example at 13:31

[@DineshVutukuru]

07:48, you can use Switch case. It's little better than nested If else loops.

[@saipratapdannana8048]

How much can we demand as front end developer with 1 year experience?

[@RoadsideCoder]

Minimum 15 LPA

[@gurmandeep4417]

Can u please tell how to solve a error while making a project

[@kritigoel3854]

Hi @RoadsideCoder , with infinite currying code, its returning only Function ..not the addition, Could you please clarify. function add(a){ return function(b){ if(b) return add(a + b); return a; } } console.log(add(4)(5)(7)); OUTPUT: [Function]

[@sandyGamer97]

it is returning function because you should call like this console.log(add(4)(5)(7)()) ; without (), function does not get invoked and you get only function body

[@pkyadav6230]

Subscribed❤

[@lifeisbeautifu1]

Thank you

[@Abhishekverma-yj1or]

My Interview asked me this question -> Write a function sum that takes n arguments and can be called n times. Note - Function can take n arguments and can be called n times. For example - sum(1,3,5,1)(1,2,3,4,5)(1)(1,2)(1,1,1,1,1,1)(1,4,5)(12)(11)(50, 51, 52) console.log(sum.....) => 221 It was for SDE - 1 Role. I still not able to understand this problem.

[@Abhishek_Sawant]

const infiniteSum = (...a) => { return (...b) => { const currSum = [...a, ...b].reduce((sum, val) => sum + val, 0); return b.length ? infiniteSum(currSum) : currSum; }; };

[@Abhishekverma-yj1or]

@@Abhishek_Sawant Hey thanks man :)

[@Abhishek_Sawant]

@@Abhishekverma-yj1or 👍😅

[@sandyGamer97]

function sum(...args){ let a = args.reduce((a,b)=>a+b,0); return function (...args){ let b = args.reduce((a,b)=>a+b,0); if(b) return sum(a+b); return a; } }

[@kashmirtechtv2948]

In manipulating DOM example, why don't we simply create a fucntion instead of returning a fucntion

[@Frank-vm7vm]

Bhai Make video on spread operator tricks

[@biswajitchanda6592]

const sum = function(a) { return function(b) { if (b) { return sum(a + b); } else { return a; } } } yes we can write that in one line: const add = a => b => b ? add(a + b) : a;

[@pavithrasai1392]

how much can we demand for frontend developer role with 3.9 yrs of experience?

[@RoadsideCoder]

Depends on your skills, sky is the limit.

[@pavithrasai1392]

​@@RoadsideCoder I have experience and knowledge in JS, ReactJS and React Native

[@HemantKumar-dl9wh]

Hi, I've written below code. Is it write wrt to currying?' const evalute = a => { switch (a) { case 'sum': return function (b) { return function (c) { return b + c; }; }; case 'sub': return function (b) { return function (c) { return b - c; }; }; default: break; } }; console.log(evalute('sum')(5)(3)); console.log(evalute('sub')(5)(3));

[@ashishprasad2163]

Follow dry(Don't Repeat Yourself)

[@kewalkandpal]

🔥🔥🔥

[@akash_gupta_2090]

done ... !

[@NirajKumar-j4m4r]

This will give you an error when you pass b=0 to handle all cases use below code function add(a) { return function (b) { return b >= 0 ? add(a + b) : a; }; } console.log(add(1)(2)(4)(0)());

[@santrawebtech35]

how are you sir please make a project on MERN as like dosti chat app

[@RoadsideCoder]

Sure :)

[@santrawebtech35]

@@RoadsideCoder thanks love you sir

[@kashmirtechtv2948]

Now i am confused between Closure and Currying 😅

[@eelguneezmemmedov1671]

Please put the on github sir .

[@ambupadamuduli3794]

Bro jaldi jaldi video daalo

[@Cuddlehead]

*okay cool*

[@anushajammula9837]

I want theory related and code based questions with pdf

[@RoadsideCoder]

Sure, I'll create a github repository for it!

[@jaisharma545]

now legends will only subscribe you because of "69" years of goodluck 🤣

[@RoadsideCoder]

Are u that legend?

[@jaisharma545]

@@RoadsideCoder yes I am😂 and thank you from the depth of my heart. for creating such awesome content 💙

[@RoadsideCoder]

@@jaisharma545 welcome 🙏

[@vishalmishra1937]

0:31 🤣

[@bhushanbhale3309]

Why 69 years of goodluck..... means why 69 only 😁😁😁