Back-End Programming Exam > Back-End Programming Videos > The Complete NodeJS Developer Course > Node.js Tutorial for Beginners - 18 - Understanding app.js
Node.js Tutorial for Beginners - 18 - Understanding app.js Video Lecture | The Complete NodeJS Developer Course - Back-End Programming
FAQs on Node.js Tutorial for Beginners - 18 - Understanding app.js Video Lecture - The Complete NodeJS Developer Course - Back-End Programming
| 1. What is Node.js and why is it popular for back-end programming? |  |
Ans. Node.js is a runtime environment that allows developers to run JavaScript on the server-side. It is popular for back-end programming because:
- It uses an event-driven, non-blocking I/O model which makes it highly efficient and scalable.
- It allows developers to use the same language (JavaScript) for both front-end and back-end development, simplifying the development process.
- It has a large and active community, with a vast ecosystem of libraries and modules that can be easily integrated into Node.js applications.
- It is lightweight and has a small memory footprint, making it suitable for handling a large number of concurrent connections.
| 2. How does Node.js handle concurrent connections? | |
Ans. Node.js uses an event-driven, non-blocking I/O model to handle concurrent connections. Instead of creating a new thread for each connection, it uses a single thread to handle multiple connections asynchronously. When a connection is made, Node.js registers a callback function to be executed when the I/O operation is completed. This allows Node.js to efficiently handle a large number of connections without blocking the execution of other operations.
| 3. What is app.js in Node.js and what is its role in back-end programming? | |
Ans. In Node.js, app.js is a common name given to the main file that initializes and configures the application. It acts as the entry point for the back-end application. The role of app.js is to set up the server, define routes, middleware, and other configurations required for the application to function. Developers can define custom logic in app.js to handle requests, perform database operations, and implement other back-end functionality.
| 4. How can I create a basic server using Node.js and app.js? | |
Ans. To create a basic server using Node.js and app.js, you can follow these steps:
1. Install Node.js on your machine if you haven't already.
2. Create a new directory for your project and navigate to it in the terminal.
3. Run the command `npm init` to initialize a new Node.js project.
4. Install the Express framework by running `npm install express`.
5. Create a new file named app.js and open it in a text editor.
6. Import the Express module by adding `const express = require('express');` at the top of the app.js file.
7. Create an instance of the Express application by adding `const app = express();` below the import statement.
8. Define a route handler for the root URL by adding `app.get('/', (req, res) => { res.send('Hello, World!'); });` below the previous line.
9. Start the server by adding `app.listen(3000, () => { console.log('Server is running on port 3000'); });` at the end of the file.
10. Save the file and run `node app.js` in the terminal to start the server. You should see the message "Server is running on port 3000".
11. Open your web browser and navigate to http://localhost:3000. You should see the message "Hello, World!" displayed in the browser.
| 5. Can I use app.js for front-end programming in Node.js? | |
Ans. No, app.js is primarily used for back-end programming in Node.js. It is responsible for setting up the server, handling requests, and implementing server-side logic. For front-end programming, which involves creating user interfaces and handling client-side interactions, you would typically use JavaScript frameworks like React, Vue.js, or Angular. These frameworks are designed specifically for front-end development and provide features and tools to build interactive web applications.
Text Transcript from Video
all right house is what I want to do in
this video is I actually want to clean
up this default project even more and by
that I mean remember we got a home page
and also this user's page whenever we
first started but we actually don't even
need this users page so let me just rip
out the code to uh you know make
everything a little bit more simple so
let's see what code we don't need in
this fjs file first delete this favicon
because we all be worrying about the
favicons right now and also the line
number eight which i guess would be why
number nine before I deleted that but
again this is just a requirement to that
users file that we're going to be
getting rid of and let's see what else
right here alright so in line 24 which
would have been 26 delete the line for
the users because again we're going to
be deleting that file and we of course
can't use that middleware if it doesn't
exist so delete those three lines of
code right there and also this user's
route right click it and delete it okay
so right now of course we don't have any
users page just the home page and to
verify that if I restart this and try to
go to users refresh it it doesn't exist
so exactly what I wanted one single page
I think it'll be a little bit easier to
explain if we don't have you know all
that extra crap all right so in fjs
let's figure out what everything does
alright so we already know what this
stuff is Express we learned about that's
what we're using path we already learned
about that in it was like really early
like a third tutorial whatever pretty
much working with file paths
what are these other ones logger is
actually a module used for logging out
info in the terminal so for example you
see this right here it was logged out
through the use of logger which they
named Morgan I don't know why but they
did it whatever probably the Creator was
named Morgan or something and now we're
getting off track so let's continue
alright so cookie parser you can
probably already guess is for handling
cookies body parser whenever you have to
parse a text body or adjacent part or
Jason body say party I'll be cool Jason
party whatever all right then that's
what you use routes we already know that
is pretty much the brains behind
everything now this line of code you
could probably understand from our
connect tutorial what this does is it's
pretty much initializing your app to use
Express in other words we're saying let
Express and let this framework handle
all of the user requests this little
chunk of code right here is setting up
how the views are handled and if we
chose um Jade for like when we were
first setting up our project then it
would of course use the Jade as the view
engine but we're using EGS and again I'm
going to be explaining you guys exactly
how to use ejs in well probably the next
tutorial but yeah all right so this look
little chunk of code we're going to see
you later as well it's just setting up
how data is logged in parsed this right
here is looking at your path for example
we only have one page right now so not a
whole lot of options
let's saying whenever the user requests
this page using that path and use this
middleware which is essentially index
touch is now if you guys are wondering
ah right what's up with all of these
error handlers well what this little
chunk of code does is it as you can see
it catches the 404 error and it passes
on to the next error handler so just
like a stack know I've got like a chunk
in my throat so that's why it calls next
passing in eerr because it's passing it
through the stack and if we ever wanted
to make additional error handlers that's
why they threw this little comment right
here they say put them right there
now this little chunk of code right here
and this little chunk of code are both
error handlers in other words whenever
you're working on your project or
whenever your website is live and you
get a bug some kind of error then these
tell it how to be handled why do we have
two of them well the only difference
between these two is that you use this
one right here during development
and use this one whenever your websites
live and that's called production so why
would you need two different ones will
you just handle them the same either way
well check this out you see right here
whenever we went to the website users
well that doesn't exist anymore so what
it did is it printed out the stacktrace
in other words it printed out a detailed
message of our air so we can pretty much
find the bug now whenever our website is
live let's say that the user
I know clicks a button and something
goes wrong obviously you don't want to
be spewing out a bunch of error messages
and stack traces to them because if like
my grandma's using the saying she was
looking at this she would probably think
someone was hacking into her computer so
that's the difference between these two
during development when you're just
working on your project you actually
want to see these stack traces because
they help you find the bugs a lot easier
however during production you want to
hide those and well there you go and now
they're finally done understanding what
the heck all of these files mean we can
get into the fun stuff so thank guys for
watching don't forget subscribe see you
next time
this video is I actually want to clean
up this default project even more and by
that I mean remember we got a home page
and also this user's page whenever we
first started but we actually don't even
need this users page so let me just rip
out the code to uh you know make
everything a little bit more simple so
let's see what code we don't need in
this fjs file first delete this favicon
because we all be worrying about the
favicons right now and also the line
number eight which i guess would be why
number nine before I deleted that but
again this is just a requirement to that
users file that we're going to be
getting rid of and let's see what else
right here alright so in line 24 which
would have been 26 delete the line for
the users because again we're going to
be deleting that file and we of course
can't use that middleware if it doesn't
exist so delete those three lines of
code right there and also this user's
route right click it and delete it okay
so right now of course we don't have any
users page just the home page and to
verify that if I restart this and try to
go to users refresh it it doesn't exist
so exactly what I wanted one single page
I think it'll be a little bit easier to
explain if we don't have you know all
that extra crap all right so in fjs
let's figure out what everything does
alright so we already know what this
stuff is Express we learned about that's
what we're using path we already learned
about that in it was like really early
like a third tutorial whatever pretty
much working with file paths
what are these other ones logger is
actually a module used for logging out
info in the terminal so for example you
see this right here it was logged out
through the use of logger which they
named Morgan I don't know why but they
did it whatever probably the Creator was
named Morgan or something and now we're
getting off track so let's continue
alright so cookie parser you can
probably already guess is for handling
cookies body parser whenever you have to
parse a text body or adjacent part or
Jason body say party I'll be cool Jason
party whatever all right then that's
what you use routes we already know that
is pretty much the brains behind
everything now this line of code you
could probably understand from our
connect tutorial what this does is it's
pretty much initializing your app to use
Express in other words we're saying let
Express and let this framework handle
all of the user requests this little
chunk of code right here is setting up
how the views are handled and if we
chose um Jade for like when we were
first setting up our project then it
would of course use the Jade as the view
engine but we're using EGS and again I'm
going to be explaining you guys exactly
how to use ejs in well probably the next
tutorial but yeah all right so this look
little chunk of code we're going to see
you later as well it's just setting up
how data is logged in parsed this right
here is looking at your path for example
we only have one page right now so not a
whole lot of options
let's saying whenever the user requests
this page using that path and use this
middleware which is essentially index
touch is now if you guys are wondering
ah right what's up with all of these
error handlers well what this little
chunk of code does is it as you can see
it catches the 404 error and it passes
on to the next error handler so just
like a stack know I've got like a chunk
in my throat so that's why it calls next
passing in eerr because it's passing it
through the stack and if we ever wanted
to make additional error handlers that's
why they threw this little comment right
here they say put them right there
now this little chunk of code right here
and this little chunk of code are both
error handlers in other words whenever
you're working on your project or
whenever your website is live and you
get a bug some kind of error then these
tell it how to be handled why do we have
two of them well the only difference
between these two is that you use this
one right here during development
and use this one whenever your websites
live and that's called production so why
would you need two different ones will
you just handle them the same either way
well check this out you see right here
whenever we went to the website users
well that doesn't exist anymore so what
it did is it printed out the stacktrace
in other words it printed out a detailed
message of our air so we can pretty much
find the bug now whenever our website is
live let's say that the user
I know clicks a button and something
goes wrong obviously you don't want to
be spewing out a bunch of error messages
and stack traces to them because if like
my grandma's using the saying she was
looking at this she would probably think
someone was hacking into her computer so
that's the difference between these two
during development when you're just
working on your project you actually
want to see these stack traces because
they help you find the bugs a lot easier
however during production you want to
hide those and well there you go and now
they're finally done understanding what
the heck all of these files mean we can
get into the fun stuff so thank guys for
watching don't forget subscribe see you
next time
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Dec 23, 2024 Last updated |
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