Node.js – REPL

REPL stands for Read, Eval, Print, and Loop. Node.js also provides a REPL environment for quicky testing and debugging Node.js code.

You can also store all the commands executed on Node REPL by setting the NODE_REPL_HISTORY environment variable. Node.js REPL will store all commands to the file set with this variable

export NODE_REPL_HISTORY=/var/log/node-repl.log

Use CTRL + C + C to exit from REPL console.

Start REPL Console

Run command node on your system console and this will provide you REPL prompt (>) for Node.js. Where you can run and test your Node.js code quicky.

node

Working with Node.js REPL

Let’s work with the Node.js REPL interface. Start the Node.js REPL interface and run the below examples. You can also try your own example commands.

Simple Arithmetic Operations

Perform some basic arithmetic operatins on Node.js terminal. The result will be shown on the screen.

5+10 
15
10+(5*3)
25

Using Variables

Now try with some variables. For example store values in two variable and try a simple calculation, You will see the result on screen. You can simply assign a value to the variable like below example.

a=10 
10
b=15
20
(a + b)/2
15

You can also use the var keyword to define the variable value.

var a=10 
undefined
var b=15
undefined
(a + b)/2
15

Let’s try to store a string value to the variable. After that try to print value stored in the variable using the console.log() function.

name="TecAdmin.net"
'TecAdmin.net'

 console.log(name)
TecAdmin.net
undefined