Hello World

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