Node.js REPL: The Complete Tutorial for Beginners

Node.js REPL runs JavaScript code in an instant test space inside your terminal.

What is Node.js REPL?

Node.js REPL is a console inside Node.js that reads code, evaluates it, prints the result, and waits for the next input.

The REPL reads code line by line and returns the output after each line. It gives you history for commands and direct access to Node.js modules. It also lets you use JavaScript objects and methods fast.

You can open your terminal and type node , then press enter. The prompt > appears and waits for your input.

You can write JavaScript code and press Enter to see the result at once.

REPL does not store your work after exit. It runs code line by line but cannot run files. It cannot handle heavy apps because it is for small tests only.

The Common Commands in REPL

Here are some useful commands inside Node.js REPL. Each command has a small example.

• .help
• .exit
• .save
• .load

Let’s explain each one in depth:

The .help shows you all available REPL commands. Here is an example:

.help

It prints a list of all REPL commands you can use.

The .exit closes the REPL session. For example:

.exit

It stops the current REPL session and returns to your terminal.

The .save saves your REPL session into a file. For example:

.save session.js

It writes all commands from the current REPL session into session.js.

The .load loads code from a file into REPL. Here is an example:

.load session.js

It loads all code from session.js into your current REPL session.

Node.js REPL vs Console

Node.js REPL runs live code inside a terminal. It gives instant feedback for each line. The console object in Node.js writes logs or errors from running code inside files or servers.

REPL helps developers test code blocks fast. The console object helps apps log data, debug, or show user messages. REPL works inside your terminal. Console works inside your program.

Use REPL for small experiments and test ideas, and the console for logs and debug data inside real apps.

Examples

Math in REPL:

2 + 3

This code returns 5 inside REPL at once. It shows how REPL handles direct math without extra steps.

Load a Module:

const os = require('os')
os.platform()

This code imports the os module and shows the platform name inside REPL. It helps you check system details in one step.

Save a Session:

.save mysession.js

This code writes all commands from your current REPL session into a file named mysession.js for later use.

Load a Saved Session:

.load mysession.js

This code loads a saved REPL session back into the console so you can continue from the same point.

Wrapping Up

You learned what Node.js REPL is and how it works. You also saw how to start it, use common commands, and compare it with the console.

Here is a quick recap:

• Node.js REPL runs live code inside your terminal.
• It gives instant results.
• You can save sessions, load files, and use built-in modules.
• The console object logs data inside real apps.
• Use REPL for tests and console for app logs.

FAQs

node

> .help
> .exit

> 2 + 3
5

> let x = 10;
> let y = 20;
> x + y
30

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