Update nodejs.md

en/server-side/nodejs.md

@@ -26,6 +26,19 @@ This should print the version number of Node.js like this:
 ```bash
 v20.7.0
 ```
+## Node.js REPL
+
+REPL is a command line interface that stands for Read Evaluate Print Loop, which enables you to run code from the terminal. To get started, type the following command into your terminal:
+
+```bash
+node
+```
+Once you enter this prompt, you can run code, like this:
+
+```js
+> console.log("Hello World")
+```
+You can leave the REPL by typing CTRL + d
 
 ## Writing your first Node.js program
 
@@ -51,7 +64,13 @@ Hello World!
 
 Express is a popular web framework for Node.js. It provides a simple and elegant API for building web applications. Let's use Express to create a simple web server that will respond to HTTP requests with a "Hello World!" message.
 
-First, we need to install Express. To do this, run the following command in your terminal:
+First, we need to initialize npm by running npm init.
+
+```bash
+npm init
+```
+
+Then, install express
 
 ```bash
 npm install express