Higher Order Function | javascript interview series
Summary
TLDRIn this video, the host delves into the concept of higher-order functions in JavaScript, emphasizing their importance in interviews. He explains that higher-order functions either take a function as an argument or return a function. The video highlights practical examples, such as setTimeout and array filter methods, to illustrate the concept. Additionally, the host advises candidates to share personal experiences and project implementations to make their answers more engaging and impressive to interviewers. The goal is to transform the interview into a discussion, showcasing not just knowledge, but practical understanding and application of higher-order functions.
Takeaways
- 📚 A higher order function in JavaScript is defined as a function that takes another function as an argument or returns a function.
- 🔍 The candidate's eagerness to answer the definition from MDN is noted, but interviewers seek a deeper understanding and personal experience with higher order functions.
- 💡 The script suggests starting explanations with code examples to illustrate the concept of higher order functions, such as using `setTimeout`.
- 👨🏫 The importance of turning an interview question into a discussion is emphasized, sharing personal stories and experiences with higher order functions.
- 🔑 The script uses `filter` as an example of a higher order function, explaining how it processes arrays based on a provided function.
- 🛠️ The benefits of higher order functions include writing less code, improving readability, and making code more maintainable.
- 📈 The script provides an example of creating an `asyncHandler` to streamline error handling and database interactions in a project.
- 🔄 The `asyncHandler` example demonstrates how functions can be treated as variables, passed around, and composed to create more complex functionality.
- 📝 The candidate is encouraged to share specific use cases from their own projects to showcase their understanding and application of higher order functions.
- 🚀 The script concludes by advising candidates to focus on storytelling and personal experiences with higher order functions to impress interviewers.
- 👋 The video ends with an invitation to subscribe for more interview tips and to stay tuned for the next video in the series.
Q & A
What is the definition of a higher order function according to the video?
-A higher order function is a function that takes another function as an argument or returns a function.
Why is it important to discuss higher order functions in a JavaScript interview?
-Higher order functions are a common practice in JavaScript and discussing them can demonstrate a candidate's understanding and practical experience with functional programming concepts.
What is the first example of a higher order function given in the video?
-The first example given is 'setTimeout', which is a function that takes another function as an argument to execute after a specified delay.
How does the video suggest explaining the concept of higher order functions during an interview?
-The video suggests explaining higher order functions with code examples, starting with basic examples like 'setTimeout', and then moving on to more complex examples like using 'filter' and 'reduce'.
What is the advantage of using higher order functions in coding?
-Higher order functions allow for writing less code that is more readable, maintainable, and can be easily reused and modified.
Can you provide an example of how to use the 'filter' method as a higher order function?
-The 'filter' method can be used to process an array, for example, to filter out salaries above a certain value by providing a function that checks if each element meets the condition.
What is the purpose of creating an asyncHandler in the context of the video?
-The asyncHandler is created to simplify error handling and to avoid repetitive code when interacting with databases, making the code more efficient and less prone to errors.
How does the video suggest using higher order functions to improve the asyncHandler example?
-By treating functions as variables that can be passed and returned, the asyncHandler can wrap any function in a try-catch block and convert it to an async function, making it more versatile and error-resistant.
What is the significance of the 'useHandler' function in the asyncHandler example?
-The 'useHandler' function is significant because it demonstrates how to pass a function as an argument to another function, which then processes it within an async context and error handling, showcasing the power of higher order functions.
How can a candidate impress interviewers with their understanding of higher order functions?
-A candidate can impress interviewers by not only defining higher order functions but also by narrating a story of their first encounter with the concept, explaining how they implemented it in projects, and discussing its advantages.
What is the final advice given in the video for candidates preparing for a JavaScript interview?
-The final advice is to focus on understanding and being able to explain higher order functions with practical examples and use cases, which can demonstrate a well-versed programming skill set.
Outlines
📘 Understanding Higher Order Functions in JavaScript
This paragraph delves into the concept of higher order functions in JavaScript, which are functions that either take another function as an argument or return a function. The speaker emphasizes the importance of not just knowing the definition from MDN, but also being able to discuss the first time the concept clicked and how it has been implemented in practice. The paragraph provides examples like 'setTimeout' to illustrate higher order functions and encourages interviewees to share a story that demonstrates their understanding and use of the concept, rather than just repeating definitions.
🔍 Practical Applications of Higher Order Functions
The speaker provides practical examples of higher order functions, such as the 'filter' method in JavaScript, which processes arrays based on a provided function. The paragraph explains how higher order functions can lead to more concise, readable, and maintainable code. It also discusses the advantages of using higher order functions, like chaining 'filter' methods and the ability to pass functions as parameters to other functions, as demonstrated in the creation of an async handler for database interactions. The paragraph encourages interviewees to share their own experiences using higher order functions in projects to impress interviewers.
🚀 Enhancing Code with Higher Order Functions
This paragraph continues the discussion on higher order functions, focusing on how they can be used to create more efficient and error-free code. The speaker uses the example of an async handler that wraps database calls in try-catch blocks to prevent errors from propagating. The paragraph highlights the beauty of higher order functions in allowing developers to pass functions as variables and return them from other functions, leading to cleaner and more modular code. It concludes with advice for interviewees to share specific use cases from their projects to demonstrate their proficiency with higher order functions.
Mindmap
Keywords
💡Higher Order Function
💡MDN
💡Interview
💡setTimeout
💡Filter
💡Closure
💡Front-end Developer
💡Back-end Developer
💡Async Handler
💡Express
💡Try Catch
Highlights
Introduction to the concept of higher order functions in JavaScript.
The importance of not just knowing the definition but also being able to discuss and demonstrate higher order functions.
Definition of higher order functions according to MDN: functions that take other functions as arguments or return a function.
The need to share a personal story or experience with higher order functions to impress interviewers.
Explanation of how to use higher order functions with code examples.
The use of setTimeout as an example of a higher order function.
Demonstration of how functions can be treated as variables in higher order functions.
The advantage of using higher order functions for writing less and more readable code.
The use of filter as a higher order function to process arrays.
Chaining higher order functions for more complex logics.
The practical application of higher order functions in a project for async handling.
Creating a syncHandler utility function to reduce repetitive code.
The process of converting a regular function into a higher order function step by step.
Incorporating higher order functions into middleware for error handling in Express.
Wrapping functions with try-catch for robust error handling using higher order functions.
The importance of understanding and being able to explain the practical use of higher order functions in interviews.
Encouragement to narrate a story with higher order functions to stand out in interviews.
Advice for those who have not built anything with higher order functions to prepare well for interviews.
Transcripts
hey there everyone they share back again
with another video and in this video we
are continuing our JavaScript interview
series yes I kind of got laid into it
but here is another question for you
what is a higher order function the
moment a candidate gets a question that
what is a higher order function he just
get started a higher order function is a
function that takes function as a
parameter auditor I really understand
that you are very eager to answer the
definition which is given on the mdn and
to be honest let me just show you that
what it is so if you go up here onto the
mdn docs you'll find that there is a
note that what higher order function
should be considered or what that is if
you go up here it says a function that
returns a function or takes other
function as argument as is considered as
a higher order function a perfectly well
definition but the reason why you are
not able to impress the interviewers in
this question is because you are just
answering the question which is a good
thing but the best interviews are the
ones which eventually get converts into
a discussion the interviewer also knows
that this is the definition of higher
order function but his intention mostly
are is to get to know that when was the
first time it clicked that it is a
higher order function
and when did the first time you actually
implemented or used it whether you're
coming up from a front-end developer
back-end developer this is such a common
practice that's why it appears so many
times in the interview so you should
really portray down a story which
obviously explains the topic just stay
on the high order function don't go into
the event loops and all that thing it's
really good that you know about them you
have watched a lot of videos on YouTube
about it but try to stick on to the
higher function let me give you a
definition not just the definition a way
of explanation of how you should be
doing it as what is a high order
function for the interview perspective
so this is a higher order function you
should really start explaining such
things with the code so we have seen
functions like this so there is a
function let's just say there is a
function known as salary which takes a
number whatever the number is and it
simply go ahead and simply say that
number multiplied by 0.7 so it cuts down
the taxes and only gives you 70 percent
this is a perfectly fine function in but
it cannot be considered as higher order
function simple reason this is taking a
number and giving me a value by
processing it it might take an ID and
might just query the database and give
us the value so what is a higher order
function according to the definition or
according to the definition made by
programmers it should either take a
value which is a function or returns a
value which is a function so the example
should be given up started by the very
first and the basic that if higher order
function you want to talk about set
timeout is one of the higher order
function because it it just verifies all
the check marks which is there so set
timeout is a function or an API
which uh you cannot actually work with
it without being a high order function
because you are telling the set timeout
that hey wait for x amount of time and
then do this task for me and task is
always a set of instruction that you are
providing him so obviously you have to
provide a function to it and in order to
execute that you are saying that hey
this much amount of time you wait now
you obviously can write a function up
here or you can just say hey just go
ahead and use a salary and just wait for
300 times here now this salary obviously
you know that please don't execute it
because that's a bad one you are now
passing up the return value into the set
timeout which obviously you know from
the last video of the closure that we
discussed but you should be passing a
reference that wait for some time and
then do this so this is all higher order
function when you treat your functions
as just like variables it can be passed
on it can be returned as that is a
higher order function I understand this
is a little bit uh too much to digest
for people who are coming up from Lang
languages like C C plus plus we have
never treated functions like this in the
past so this is good now once you
actually explain this all about as a set
timeout which is always a good
indication that how well you understand
so you are taking examples not from high
end but from the very basic which is set
timeout then try to jump into something
like uh let's just say uh we are going
to create a variable uh let's just call
this one as my salaries
whatever they are and this is a variable
not available in arrays so let's just
get values 50 and 40 and 60 and 20 and
then we have 300 400 so don't take too
much long values but these are the
values that we have
now these values right now they are
numbers but they could be values that
are coming up from the database and
obviously you want to process these
values so for example uh maybe you want
to say that hey my salaries I want to
filter the values which are above 50. so
I'm going to just use a filter value and
now there is no way to tell this filter
function that what I want I have to
provide a function which executes
something and give me a result so this
also can obviously be considered as
higher order function and here you can
just simply go ahead and write a
mechanism that hey this is how it's
going to do this so filter actually
takes and loop through all the values
when let's just call each value as n you
can use your regular functions or you
can use these Arrow functions as well
and I'm going to say that n is greater
than 50. so only those values will be
returned to me now obviously I'm not
going to go ahead and do a console log
here because that is too basic here is
the interview series you know what the
result is going to be but why one should
do this why there is a filter that needs
to be used we can go through and do this
with the regular methods like loops and
all these things yes you can do it but
the advantage that you get with the
filter is that you are only focusing on
the Logics and these Logics can be
changed one good example is you can just
keep on chaining these filters can keep
on writing the Logics and then finally
Loop throughout and do the things this
is one of the example that will impress
that using the higher order functions we
are writing very less amount of code
and this code is easy readable
maintainable and going up nicely for
example here in the salaries you want to
do some functions so just pass on the
reference for example you will just pass
on a reference of salary here and here
you will pass on something like a text
so you are calculating the text values
and then you Loop through and do the
things so how easy and readable the code
becomes now because we are using higher
order function that is one of the
advantage here now once you are done
explaining these things like filters and
reduce don't stop there try to explain
that that the first time it clicked to
me and the first time I use it try to
give an example which you have used in
the project and obviously if you have
worked on any project you'll use it like
while the project we did in our first
batch was we wanted to write an async
Handler so the thing handler was
something like this that hey this is a
const and a sync Handler so that we want
to do now why we wanted to build in a
sync Handler the obvious use case in
front of us is we were are interacting
so much with the database and whenever
you interact with the database you have
to use a sync or you probably want to
use a try catch or probably both and
writing those try catch thing again and
again and again will just make our code
files lengthy just like here you can do
all these Logics via Loops but Loops
will take their own space and inside the
loop all you're going to write is the
logic itself so that's why it saves time
this async Handler one utility being
designed outside of the controllers
saved us a lot of line of code so I said
how can we write this a thing Handler so
I just say that hey how do we write the
regular function first let's go through
with that and step by step understand it
so first is this is how you write your
error function great nice there is no
problem in it at all now how can I
convert this so that it accepts function
as a parameter I can go ahead and say
hey accept FN or Fung whatever you like
to call this and this is how it goes
nice and easy the step two is pretty
easy now can I go ahead and pass on this
into a second function so can I do this
so for example I can go ahead and say
hey this is my function and now this
function will do something like this so
for example I go ahead and say hey this
is a narrow function but further is
being processed by somebody and there we
go
now this is only possible because of the
first example in the line 9 this is the
use case we are considered this function
and whatever the output of this you are
just sending it to another one and
understanding this line will actually
take some time but once you click it
that's exactly where you can answer what
is a higher order function now further
down the line what you can do is you can
just go ahead and come up and say hey I
want to make an a sync function just
like this so I'll just use in a sync so
notice how you were able to take a
function and step by step you are able
to treat that function as just a
variable and then after that you just
passed on whatever the result is into
this second function this is exactly
like line number nine we are trying to
do that and now then we are going to go
ahead and simply uh going ahead and
writing in a sync function let me just
go ahead and write this a sync
controller function here so that you
understand what all this actually boils
down and will give you a little bit more
advantage of higher order function and
how it works actually so in this one we
are taking a function as whoever calls
the sync Handler and then we want to use
in a sync so just like in the line
number 15 we are saying so a sync and
what we did in that is request response
and probably go through with the next
this is a little bit of a code from
Express and writing middlewares of it
but don't you worry on that now once we
have this what the whole thing I wanted
to do is wrap everything around the try
catch so in this I simply go ahead and
say hey await and whatever the function
you are passing me
I'm going to go ahead and say request a
response and next
so notice the beauty of this code what
we have in front of us is that anybody
who calls using Handler can just be
absolutely very free can pass me on
function I'll convert that function into
a sync and of eight not only that I'll
wrap it up with a tricad so that makes
my database called really really uh
error free or I'm just handling the
cases here here I can write my catch
cases and here I can just go with that
now if you are able to explain this much
this gives one of the use case that you
have actually used the higher order
function there you are not just
repeating the information which is
available in the mdn and this will
eventually convert into a simple uh kind
of a discussion that hey this guy
actually not only understand the higher
order function this guy understands
what's the implementation are this guy
also one have used it actually into some
of the projects so he is a well-versed
programmer so try to focus not only just
be with these basic examples that filter
is a type of a higher order function or
set timeout as one try to narrate it
with a story by story thing and then you
will obviously be able to impress the
interviewer as well as you will
thoroughly explain him what a higher
order function is with a use case that
you have used in the code but in case
you have never built anything good luck
with them in that case so that's my
brief uh two cents in making sure that
you crack your interview let's catch up
in the next video hope you have already
subscribed to the channel
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