The Node.js REPL

The REPL (Read Eval Print Loop) is an interactive shell that comes with Node.js. It reads what you type, evaluates it, prints the result, and waits for more. It is perfect for quick experiments.

Starting the REPL

Type node in your terminal with no file name and press Enter. You will see a > prompt where you can type JavaScript.

Trying expressions

// At the > prompt
2 + 3            // 5
"hi".toUpperCase()  // 'HI'
const x = 10
x * x            // 100

The REPL prints the value of each expression automatically.

Useful commands

• .help shows all REPL commands.
• .clear resets the current context.
• .exit quits the REPL (or press Ctrl+C twice).

The special variable _

The underscore holds the result of the last expression:

5 * 5   // 25
_ + 1   // 26

Summary

The REPL is a fast playground for testing small pieces of code without creating a file. Use it to learn and explore the language.