What is REPL in Node.js?

Understanding the Read-Eval-Print Loop.

What You'll Learn

What REPL is
How to use it
Useful commands

What is REPL?

REPL stands for Read-Eval-Print Loop. It's an interactive shell to execute JavaScript code.

Starting REPL

$ terminalBash

# Start Node REPL
node

# You'll see
>

Using REPL

code.jsJavaScript

> 2 + 2
4

> const name = 'Node'
undefined

> console.log(name)
Node
undefined

> [1,2,3].map(x => x * 2)
[ 2, 4, 6 ]

REPL Commands

code.jsJavaScript

.help    - Show help
.break   - Exit multi-line input
.clear   - Clear context
.exit    - Exit REPL
.save    - Save session to file
.load    - Load file into session

// Special variable
_        - Last result

Example

code.jsJavaScript

> 5 + 5
10
> _ * 2
20
> .save session.js
Session saved to: session.js

What are Global Objects in Node.js?

How to work with the File System (fs) module?