1
00:00:00,850 --> 00:00:03,552
Who says back-end programs
can't be interactive?

2
00:00:03,552 --> 00:00:08,032
In this program, we'll learn different
ways to give input and output with Node.

3
00:00:08,032 --> 00:00:10,892
One way we can do this
is by using the REPL.

4
00:00:10,892 --> 00:00:13,885
This stands for read-evaluate-print loop.

5
00:00:13,885 --> 00:00:18,412
The REPL is an interactive programming
environment that can read our input,

6
00:00:18,412 --> 00:00:24,230
evaluate its meaning, print out feedback,
and loop over this process as needed.

7
00:00:24,230 --> 00:00:27,910
Node can function as a REPL
with a single command.

8
00:00:27,910 --> 00:00:32,907
Node is terminal based, so open up your
terminal to try out the Node REPL.

9
00:00:32,907 --> 00:00:36,946
If you're using workspaces,
Node will already be installed.

10
00:00:36,946 --> 00:00:41,870
We'll type Node, a caret or
greater than symbol should appear.

11
00:00:41,870 --> 00:00:46,630
And now you can write JavaScript code
that Node will interpret and respond to.

12
00:00:46,630 --> 00:00:49,670
Remember, JavaScript has
the ability to do math.

13
00:00:49,670 --> 00:00:52,850
We can enter an equation in the REPL and
get our answer.

14
00:00:53,850 --> 00:00:55,240
Let's try something really hard.

15
00:00:57,198 --> 00:01:02,548
2 + 2,
Node already knows that the answer is 4.

16
00:01:02,548 --> 00:01:04,604
We can also define variables.

17
00:01:04,604 --> 00:01:08,844
Use let favoriteMovie,

18
00:01:08,844 --> 00:01:13,767
make sure I use proper camelCase,

19
00:01:19,961 --> 00:01:23,210
I'm gonna type in favoriteMovie again,
I get the value 'lionKing'.

20
00:01:24,900 --> 00:01:26,980
We don't have a DOM to work with.

21
00:01:26,980 --> 00:01:28,520
But remember those host objects.

22
00:01:29,660 --> 00:01:33,480
Node has host objects including its
own version of the console object.

23
00:01:34,530 --> 00:01:44,112
We can console.log,
our favorite movie variable,

24
00:01:44,112 --> 00:01:49,524
and it prints out the value lionKing
to the console or terminal.

25
00:01:49,524 --> 00:01:53,893
Input and output like this shows us
some of the capabilities of Node.

26
00:01:53,893 --> 00:01:58,877
But one thing that makes Node great is
its ability to run programs in JavaScript files.

28
00:01:59,413 --> 00:02:04,199
With Node we can execute a program using
the node command followed by the name of

29
00:02:04,199 --> 00:02:05,080
the program.

30
00:02:06,090 --> 00:02:11,187
Let's create a directory
with the mkdir keyword.

31
00:02:13,274 --> 00:02:20,248
And we should probably first exit
the REPL, by pressing Ctrl + C twice.

32
00:02:24,011 --> 00:02:31,708
Now again, we'll create
a directory named nodePractice.

33
00:02:31,708 --> 00:02:33,612
Change into that directory.

34
00:02:38,817 --> 00:02:43,260
And we'll open up visual studio
code to start writing our files.

35
00:02:43,260 --> 00:02:48,907
We'll create an app.js file.

36
00:02:48,907 --> 00:02:54,487
And inside the file,
we'll type console.log.

37
00:02:58,032 --> 00:03:03,365
Our favorite programming phrase,
("Hello World") and save.

38
00:03:05,109 --> 00:03:10,057
Back in the console,
you can type node app.js,

39
00:03:10,057 --> 00:03:15,670
and Hello World is printed
out to the console.

40
00:03:15,670 --> 00:03:18,810
Node can do a lot more than just
print messages to the screen.

41
00:03:18,810 --> 00:03:22,222
You've just learned two ways we can use
Node to work with JavaScript outside of

42
00:03:22,222 --> 00:03:23,330
the browser.

43
00:03:23,330 --> 00:03:26,930
And this is a tiny sample of
what Node is capable of doing.

44
00:03:26,930 --> 00:03:29,990
We'll learn about more tasks
like connecting to an API, and

45
00:03:29,990 --> 00:03:32,570
retrieving useful information
in the next steps.