Try Node.js

5 minutes

In this unit, you'll create and run a Hello World Node.js script.

Node.js REPL

Node.js has a built-in read-eval-print loop (REPL) mode that's useful for quick code evaluation and experimentation. REPL mode is an interactive console environment where you can enter JavaScript code and have Node.js interpret and run the code and then print the output.

The Node.js REPL mode works as follows:

Read: Reads and parses the user's JavaScript code input (or shows an error if the code is invalid).
Eval: Evaluates the entered JavaScript code.
Print: Prints the computed results.
Loop: Loops and waits for the user to enter a new command (or exits if the user enters ctrl-c twice).

To start REPL mode, run the node program in Azure Cloud Shell.

Note

Use right-click > Paste to enter a copied command in Cloud Shell or in the REPL console.

node

The REPL environment opens. You should see the REPL prompt:

Enter the following code in the REPL console (right-click > Paste):

console.log('Hello World, from the REPL.')

This code prints a "Hello World, from the REPL." message in the REPL console:

Hello World, from the REPL.

To exit the REPL console, enter Ctrl + C twice.

Create a Node.js script

Node.js also supports running code from files.

In Azure Cloud Shell, open a new editor by entering the code command:
```
code
```
In the Cloud Shell code editor, create a file by entering the following code:

Note

Use Ctrl + V to enter a copied command in the Cloud Shell code editor.
```
console.log('Hello World, from a script file.');
```
Save the file with the name index.js by entering the following command:
- For Windows and Linux, enter Ctrl + S.
- For macOS, enter Cmd + S.
In Cloud Shell, enter the node command followed by the name of the file index.js:
```
node index.js
```

You should see the following output:

Hello World, from a script file.

You have now run your first Node.js JavaScript code.

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