Running Node.js and Writing Basic Scripts

Learn to run Node.js, use the Node REPL, and execute your first script.

We'll cover the following...

Running Node.js in interactive mode (REPL)
- Try it out
Writing and running our first script
- Running a script with the node command
- Try it yourself
Exercise: Using variables and simple math in Node.js
Key takeaways

Node.js is a runtime environment, so it doesn't have its own graphical interface. We interact with Node.js through a command-line interface (CLI). In this lesson, we’ll learn to run Node.js, use its interactive environment (REPL), and create a basic script. Once we’re comfortable with this, we’ll have taken our first steps into server-side JavaScript.

Running Node.js in interactive mode (REPL)

The Node.js REPL lets us interact with JavaScript directly. REPL stands for Read-Eval-Print Loop:

Read: It reads the input.
Eval: It evaluates the input as JavaScript code.
Print: It prints the result of the evaluation.
Loop: It waits for the next command.

Using the REPL is a quick way to test ideas, debug code, or try out JavaScript features. Code typed in the REPL isn't saved, so for anything you want to reuse, write a script instead. Let’s get started.