01-node-tutorial: Add tutorials based on each js file

01-node-tutorial/01-intro.md

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+## Introduction
+
+This tutorial guides you through your first Node.js application. Node.js allows you to run JavaScript outside of a web browser, on servers and command-line tools.
+
+## What is Node.js?
+
+Node.js is a runtime environment that lets you execute JavaScript code on the server-side. It's built on top of Chrome's V8 JavaScript engine and is perfect for building scalable applications.
+
+## Your First Node.js App
+
+Let's examine the code from `01-intro.js`:
+
+```javascript
+const amount = 9
+
+if (amount < 10) {
+  console.log('small number')
+} else {
+  console.log('large number')
+}
+
+console.log(`hey it's my first node app!!!`)
+```
+
+### Breaking Down the Code
+
+#### 1. **Variable Declaration**
+
+```javascript
+const amount = 9
+```
+
+- **`const`**: Declares a constant variable that cannot be reassigned after initialization
+- **`amount`**: The variable name
+- **`9`**: The initial value (a number)
+
+**Key Points:**
+- Use `const` by default (it's safer than `let` or `var`)
+- Use `let` if you need to reassign the variable
+- Avoid `var` in modern JavaScript
+
+#### 2. **Conditional Logic (if/else statement)**
+
+```javascript
+if (amount < 10) {
+  console.log('small number')
+} else {
+  console.log('large number')
+}
+```
+
+**What happens here:**
+- The `if` statement checks if `amount` is less than 10
+- If the condition is `true`, it executes the code in the first block
+- Otherwise (when condition is `false`), it executes the `else` block
+
+**In this example:**
+- Since `amount = 9`, and `9 < 10` is `true`
+- The output will be: `small number`
+
+#### 3. **Template Literals (String Interpolation)**
+
+```javascript
+console.log(`hey it's my first node app!!!`)
+```
+
+**Key Features:**
+- Uses backticks (`` ` ``) instead of quotes
+- Allows you to embed variables using `${}` syntax
+- Makes multi-line strings easier to work with
+
+**Example with variable interpolation:**
+```javascript
+const name = "Node.js"
+console.log(`Welcome to ${name}!`)  // Output: Welcome to Node.js!
+```
+
+#### 4. **Console Output**
+
+```javascript
+console.log()
+```
+
+- Prints messages to the terminal/console
+- Essential for debugging and monitoring your application
+
+## Running the Code
+
+### Prerequisites
+- Node.js installed on your computer
+- A terminal or command prompt
+
+### Steps
+
+1. **Create a file** named `01-intro.js` with the code above
+
+2. **Open your terminal** and navigate to the file's directory:
+   ```bash
+   cd path/to/your/directory
+   ```
+
+3. **Run the file** using Node.js:
+   ```bash
+   node 01-intro.js
+   ```
+
+4. **Expected Output:**
+   ```
+   small number
+   hey it's my first node app!!!
+   ```
+
+## Key Concepts Learned
+
+| Concept | Explanation |
+|---------|-------------|
+| **const** | Declares an immutable variable |
+| **if/else** | Conditional statement for decision-making |
+| **Comparison Operator (<)** | Checks if a value is less than another |
+| **console.log()** | Prints output to the console |
+| **Template Literals** | String literals that allow embedded expressions |
+
+## Practice Exercises
+
+### Exercise 1: Change the Condition
+Modify the code to check if `amount` is greater than 10:
+
+```javascript
+const amount = 9
+
+if (amount > 10) {
+  console.log('large number')
+} else {
+  console.log('small number')
+}
+```
+
+**Question:** What will be the output?
+
+### Exercise 2: Use Different Operators
+Try these comparison operators:
+- `>` (greater than)
+- `>=` (greater than or equal)
+- `<=` (less than or equal)
+- `===` (strictly equal)
+- `!==` (not equal)
+
+### Exercise 3: Multiple Conditions with else if
+```javascript
+const amount = 10
+
+if (amount < 10) {
+  console.log('small number')
+} else if (amount === 10) {
+  console.log('exactly ten')
+} else {
+  console.log('large number')
+}
+```
+
+### Exercise 4: Using Variables in Template Literals
+```javascript
+const amount = 9
+
+if (amount < 10) {
+  console.log(`${amount} is a small number`)
+} else {
+  console.log(`${amount} is a large number`)
+}
+```
+
+## Next Steps
+
+Now that you understand the basics, explore:
+
+1. **Loops** - Repeat code multiple times
+2. **Functions** - Create reusable code blocks
+3. **Objects & Arrays** - Store and manage data
+4. **File System** - Read and write files
+5. **Modules** - Import and export code
+6. **npm Packages** - Use third-party libraries
+
+## Common Mistakes to Avoid
+
+❌ **Using `var` instead of `const`/`let`**
+```javascript
+var amount = 9  // Avoid this
+const amount = 9  // Better
+```
+
+❌ **Forgetting quotes in console.log()**
+```javascript
+console.log(hey it's my first node app)  // Error!
+console.log('hey it\'s my first node app')  // Correct
+console.log(`hey it's my first node app`)  // Best (template literal)
+```
+
+❌ **Using = instead of === for comparison**
+```javascript
+if (amount = 10) { }  // Wrong! This assigns, not compares
+if (amount === 10) { }  // Correct! Compares values
+```
+
+## Summary
+
+Congratulations! You've created your first Node.js application. You've learned about:
+- ✅ Variable declaration with `const`
+- ✅ Conditional logic with `if/else`
+- ✅ String output with `console.log()`
+- ✅ Template literals for dynamic strings
+
+Continue building on these fundamentals to master Node.js!
+```
+
+This tutorial provides a comprehensive guide to your first Node.js application, covering the concepts, execution steps, and practical exercises to reinforce learning.

01-node-tutorial/02-globals.md

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+## Overview
+
+In Node.js, there are global objects and variables that are available in every module without needing to import them. Unlike browser JavaScript which has the `window` object, Node.js provides its own set of globals designed for server-side development.
+
+## Key Node.js Globals
+
+### 1. **`__dirname`** - Current Directory Path
+```javascript
+console.log(__dirname)
+```
+
+**What it does:** Returns the absolute path of the current directory containing the currently executing file.
+
+**Example output:**
+```
+/Users/username/projects/node-express-course/01-node-tutorial
+```
+
+**Common use cases:**
+- Reading files relative to the current directory
+- Setting up file paths for asset serving
+- Constructing dynamic paths for logging
+
+**Example:**
+```javascript
+const path = require('path');
+const filePath = path.join(__dirname, 'data', 'users.json');
+```
+
+---
+
+### 2. **`__filename`** - Current File Name
+**What it does:** Returns the absolute file path of the currently executing file.
+
+**Example output:**
+```
+/Users/username/projects/node-express-course/01-node-tutorial/02-globals.js
+```
+
+---
+
+### 3. **`require()`** - Module System Function
+**What it does:** Allows you to import modules using the CommonJS module system.
+
+**Example:**
+```javascript
+const express = require('express');
+const fs = require('fs');
+const path = require('path');
+```
+
+---
+
+### 4. **`module`** - Current Module Information
+**What it does:** Contains information about the current module, including exports and other metadata.
+
+**Example:**
+```javascript
+console.log(module)
+// Shows: { exports: {}, ...other properties }
+
+module.exports = { name: 'My Module' };
+```
+
+---
+
+### 5. **`process`** - Environment Information
+**What it does:** Provides information about the Node.js process and environment variables.
+
+**Common properties:**
+```javascript
+process.env       // Environment variables
+process.argv      // Command-line arguments
+process.cwd()     // Current working directory
+process.exit()    // Exit the process
+process.version   // Node.js version
+```
+
+**Example:**
+```javascript
+console.log(process.env.NODE_ENV);  // 'development' or 'production'
+console.log(process.argv);           // Array of command-line arguments
+```
+
+---
+
+## Practical Example: setInterval
+
+The code also demonstrates **`setInterval()`**, a global function for running code repeatedly:
+
+```javascript
+setInterval(() => {
+  console.log('hello world')
+}, 1000)
+```
+
+**What it does:** Runs the callback function every 1000 milliseconds (1 second).
+
+**Output:**
+```
+hello world
+hello world
+hello world
+... (repeats indefinitely)
+```
+
+---
+
+## Complete Working Example
+
+```javascript
+// Display current directory and file
+console.log('Current directory:', __dirname);
+console.log('Current file:', __filename);
+
+// Run a function every 1 second
+let count = 0;
+setInterval(() => {
+  count++;
+  console.log(`[${count}] hello world`);
+
+  // Stop after 5 iterations
+  if (count === 5) {
+    process.exit(0);  // Use process.exit() to terminate
+  }
+}, 1000);
+```
+
+---
+
+## Key Differences from Browser JavaScript
+
+| Browser | Node.js |
+|---------|---------|
+| `window` global | `global` global |
+| `document` available | No DOM |
+| Can't access file system directly | `fs` module for file access |
+| No `__dirname` or `__filename` | Both available automatically |
+| `process` not available | `process` always available |
+
+---
+
+## Summary
+
+Node.js globals are essential for:
+- ✅ Working with file paths (`__dirname`, `__filename`)
+- ✅ Managing modules (`require`, `module`)
+- ✅ Accessing environment configuration (`process`)
+- ✅ Creating timers and intervals (`setInterval`, `setTimeout`)
+
+These globals make it easy to build server-side applications without needing to import everything explicitly!