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In this video we'll create our first simple application to be run on the Node.js platform.
Commands
Running a node application
node <filename>
Running the node REPL (Read-Eval-Print-Loop)
node
To exit the REPL use CTRL+D once or CTRL+C twice.
Documentation
Node.js Installation Guide
When getting acquainted
with any new technology,
0:00
it's customary to create
a Hello World application.
0:02
We'll be using Treehouses online
coding environment work spaces.
0:06
You'll be able to write your no dress up
locations and run them in work spaces.
0:10
No need to set up your machine for
development.
0:14
If you want to use Node JS on your local
machine, I've included an installation
0:17
guide for Marco S, Windows, and
Linux in the teachers notes.
0:21
Let's click the launch workspace button
along with this video and jump right in.
0:25
Your workspace should look like this,
with a coding area at the top, and
0:30
the console or
terminal down here at the bottom.
0:34
The reason we got the terminal open here,
0:38
is because Node JS is
a terminal based application.
0:40
To make sure you've got Node JS up and
running, type node then a space -v.
0:44
Hit return, and you should see
the current version of Node JS running.
0:50
Now, don't worry if your
number is different.
0:57
It means you've got the most recent
version of node JS running in your
0:59
workspace.
1:02
You can still follow along.
1:03
Node JS, like JavaScript,
is backwardly compatible.
1:05
Anything you'll learn in this course
will be good for newer versions too.
1:09
New versions may have new features,
performance improvements, and
1:13
security updates.
1:17
Let's take a look at the file
that we have here, app.js.
1:18
Now, I've called it app.js.
1:23
Other people use a different convention.
1:25
Some people use index.js or main.js.
1:27
It really doesn't matter what you name
the file, because in order to run it,
1:32
you need to write out the filename.
1:35
To run the code in the app.js file,
type node, then
1:38
the file name, app.js, and hit enter.
1:43
And it runs the file.
1:52
Well, there's nothing there
in the file right now.
1:53
So having no output is expected.
1:56
We can clear the console as well,
by typing clear.
1:59
Hit enter.
2:04
And now we've got some
fresh space to type into.
2:05
Let's write our first Node.js application.
2:08
We can use the console object.
2:11
And the log method to print the text,
Hello world.
2:15
Be sure to include a semicolon at
the end of your line for completeness.
2:23
Save the file.
2:28
And let's head back over to the terminal.
2:30
We can press the up arrow key to
the terminal to go back to the previous
2:32
commands we've run.
2:36
Press it once, and
we see the last command clear.
2:37
Up again, and we see node app js.
2:41
Hit enter and it says hello world.
2:45
That is our first node JS application.
2:48
There's another two helpful
methods on the console object.
2:51
There's error and dir.
2:56
The error method is ideal for
logging out error messages.
3:04
Then we have the dir method.
3:13
When passing in a JSON object,
it will print out the values and
3:14
the keys in a human readable format.
3:19
The DIR function is great for
inspecting objects and
3:30
seeing what values they contain.
3:35
Save the file and
move over to the terminal.
3:38
Hit the up arrow, hit enter,
and run the app.js.
3:41
You can see that Hello world.
3:45
Oops, something went wrong and
3:48
that just an object is all printed
out in a human legible format.
3:50
Node also allows you to experiment
with JavaScript in the terminal.
3:58
Type node without any filename and
hit enter.
4:02
Doing so, brings up
an interactive JavaScript console.
4:06
A console like this is known as
a read evaluate print loop or REPL.
4:10
As it reads your code that you enter,
4:15
it evaluates it or runs it,
and then prints it out.
4:18
So I can type 1 plus 2 and
the console reads and
4:23
interprets my code and
evaluates it to 3 and prints it's out.
4:26
It can even set variables.
4:33
It can set the constant name,
to equal Andrew.
4:36
Then, when I type name,
Andrew is returned.
4:43
Now you've seen Node.js in
action in two scenarios.
4:48
Firstly, you saw that you
can write programs and then
4:51
run it with a node command and then the
filename containing the JavaScript code.
4:54
Secondly, you can play around with
node in the read eval print loop.
4:59
Where you interactively type JavaScript
code and see what the results are.
5:04
To exit the REPL you can press
Ctrl+D once or Ctrl+C twice.
5:09
What we've done is quite novel.
5:15
We've created a JavaScript
program outside of the browser.
5:17
You've written your first
Node.js application.
5:23
Writing an application in Node.js is
writing a JavaScript application, but
5:25
outside of the browser.
5:30
Let's review what we've learned about
the console in the next exercise.
5:32
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