When getting acquainted with any new technology,

it's customary to create a Hello World application.

We'll be using Treehouses online coding environment work spaces.

You'll be able to write your no dress up locations and run them in work spaces.

No need to set up your machine for development.

If you want to use Node JS on your local machine, I've included an installation

guide for Marco S, Windows, and Linux in the teachers notes.

Let's click the launch workspace button along with this video and jump right in.

Your workspace should look like this, with a coding area at the top, and

the console or terminal down here at the bottom.

The reason we got the terminal open here,

is because Node JS is a terminal based application.

To make sure you've got Node JS up and running, type node then a space -v.

Hit return, and you should see the current version of Node JS running.

Now, don't worry if your number is different.

It means you've got the most recent version of node JS running in your

workspace.

You can still follow along.

Node JS, like JavaScript, is backwardly compatible.

Anything you'll learn in this course will be good for newer versions too.

New versions may have new features, performance improvements, and

security updates.

Let's take a look at the file that we have here, app.js.

Now, I've called it app.js.

Other people use a different convention.

Some people use index.js or main.js.

It really doesn't matter what you name the file, because in order to run it,

you need to write out the filename.

To run the code in the app.js file, type node, then

the file name, app.js, and hit enter.

And it runs the file.

Well, there's nothing there in the file right now.

So having no output is expected.

We can clear the console as well, by typing clear.

Hit enter.

And now we've got some fresh space to type into.

Let's write our first Node.js application.

We can use the console object.

And the log method to print the text, Hello world.

Be sure to include a semicolon at the end of your line for completeness.

Save the file.

And let's head back over to the terminal.

We can press the up arrow key to the terminal to go back to the previous

commands we've run.

Press it once, and we see the last command clear.

Up again, and we see node app js.

Hit enter and it says hello world.

That is our first node JS application.

There's another two helpful methods on the console object.

There's error and dir.

The error method is ideal for logging out error messages.

Then we have the dir method.

When passing in a JSON object, it will print out the values and

the keys in a human readable format.

The DIR function is great for inspecting objects and

seeing what values they contain.

Save the file and move over to the terminal.

Hit the up arrow, hit enter, and run the app.js.

You can see that Hello world.

Oops, something went wrong and

that just an object is all printed out in a human legible format.

Node also allows you to experiment with JavaScript in the terminal.

Type node without any filename and hit enter.

Doing so, brings up an interactive JavaScript console.

A console like this is known as a read evaluate print loop or REPL.

As it reads your code that you enter,

it evaluates it or runs it, and then prints it out.

So I can type 1 plus 2 and the console reads and

interprets my code and evaluates it to 3 and prints it's out.

It can even set variables.

It can set the constant name, to equal Andrew.

Then, when I type name, Andrew is returned.

Now you've seen Node.js in action in two scenarios.

Firstly, you saw that you can write programs and then

run it with a node command and then the filename containing the JavaScript code.

Secondly, you can play around with node in the read eval print loop.

Where you interactively type JavaScript code and see what the results are.

To exit the REPL you can press Ctrl+D once or Ctrl+C twice.

What we've done is quite novel.

We've created a JavaScript program outside of the browser.

You've written your first Node.js application.

Writing an application in Node.js is writing a JavaScript application, but

outside of the browser.

Let's review what we've learned about the console in the next exercise.