This PR is the solution to the 'bank-project' #4

1-js-basics/solution.md

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+# Shopping Cart in JavaScript
+
+## Introduction
+
+When building a **shopping cart** in JavaScript, we use different data types to handle various aspects efficiently.Here i'll explain the **JavaScript data types** used in a shopping cart and their purposes, along with some of the examples.
+
+---
+
+## 1. Number
+
+### **Purpose of using Number :**
+
+Here i use the `Number` data type to store some of the numerical values for **product prices, quantities, and total amounts** in the shopping cart.
+
+### **Example of using Number data type :**
+
+```javascript
+let price = 299.99; // price of the single product
+let quantity = 2;    // count for the no of items added to the cart 
+let totalAmount = price * quantity; // this calculate the total cost
+
+console.log(totalAmount); // here we get the total cost 
+```
+
+---
+
+## 2. String
+
+### **Purpose of using Strings in the cart :**
+
+Here i'll use the `String` data type to store some **textual data**, such as **product names, descriptions, and categories**.
+
+### **Example usage :**
+
+```javascript
+let productName = "Wireless Headphones";
+let productDescription = "Noise-canceling Bluetooth headphoes with long battery life.";
+
+console.log(productName + " - " + productDescription);
+// Output: Wireless Headphones - Noise-canceling Bluetooth headphones with long battery life.
+```
+
+---
+
+## 3. Boolean
+
+### **Purpose of using Boolean data type:**
+
+I use the The `Boolean` data type for **true/false values** to check product **availability, stock status, and discounts**.
+
+### **Example of using Booleans:**
+
+```javascript
+let instock = true;  // here , this means that the product is available
+let onsale = false;  // this means the product Product is not on sale
+
+console.log(inStock); // Output: true
+console.log(onSale);  // Output: false
+```
+
+---
+
+## 4. Array
+
+### **Purpose of using Array:**
+
+I use `Array` data type to store **multiple items** in the shopping cart.
+
+### **Example:**
+
+```javascript
+let cart = ["Laptop", "Mouse", "Keyboard"]; 
+
+console.log(cart[0]); // Output: Laptop
+console.log(cart.length); // Output: 3
+```
+
+---
+
+## 5. Object
+
+### **Purpose of Object :**
+
+`Object` data type is used to store multiple **properties** of a product, such as its **name, price, quantity, and category**.
+
+### **Example:**
+
+```javascript
+let product = {
+    name: "Laptop",
+    price: 75000,
+    quantity: 1,
+    category: "Electronics"
+};
+
+console.log(product.name + " costs " + product.price);
+// Output: Laptop costs 75000
+```
+
+---
+
+
+## 6. Undefined
+
+### **Purpose of using undefined :**
+
+The `undefined` value is used when a **variable is declared but has no assigned value**.
+
+### **Example:**
+
+```javascript
+let discount; // value for discount is not yet set
+
+console.log(discount); // Output: undefined
+```
+
+---
+
+## 7. BigInt
+
+### **Purpose:**
+
+The `BigInt` data type is use for **very large numbers**, such as **unique order IDs**.
+
+### **Example of using Bigint:**
+
+```javascript
+let orderId = 9876543210123456789; // Large order ID
+
+console.log(orderId); // Output: 9876543210123456789
+```
+
+---
+
+## 8. Symbol
+
+### **Purpose:**
+
+The `Symbol` data type here is used to create **unique product symbols**.
+
+### **Example:**
+
+```javascript
+let productID = Symbol("Laptop"); // Unique symbol for a product
+
+console.log(productID); // Output: Symbol(Laptop)
+```
+
+---
+
+## Conclusion
+
+In a **shopping cart system**, JavaScript data types help in handling different kinds of data efficiently:
+
+| **Data Type** | **Usage in Shopping Cart**                        |
+| ------------- | ------------------------------------------------- |
+| **Number**    | Store prices, quantities, total amount of the items           |
+| **String**    | Store product names, descriptions, categories     |
+| **Boolean**   | Tracks the stock status, discounts, and availability   |
+| **Array**     | To Store multiple products in the cart               |
+| **Object**    | Store product details in a structured format      |
+| **Undefined** | for handling variables that are not initialized         |
+| **BigInt**    | Store large numerical values like order IDs       |
+| **Symbol**    | Ensure unique product identifiers                 |
+
+By using **these data types appropriately**, we can build a **efficient** shopping cart system in JavaScript! 
+
+## Second Assignment: JavaScript Functions
+
+### 1. Function That Returns a Value
+```javascript
+function calculateTotal(price, quantity) {
+    return price * quantity; // This returns the total cost
+}
+
+let total = calculateTotal(100, 2);
+console.log("Total Price:", total); // Output: Total Price: 200
+```
+
+### 2. Function That Doesn't Return Anything
+This function performs an action but doesn't return a value:
+```javascript
+function displayMessage(message) {
+    console.log("Message:", message);
+}
+
+displayMessage("Welcome to our store!"); // Output: Message: Welcome to our store!
+```
+
+### 3. Function with a Mix of Parameters and Default Values
+```javascript
+function placeOrder(product, quantity = 1, discount = 0) {
+    let pricePerItem = 500; // Assuming the price per item is 500
+    let total = (pricePerItem * quantity) - discount;
+    console.log(`Order placed for ${quantity} ${product}(s). Total: ₹${total}`);
+}
+
+placeOrder("Laptop"); // Uses default values (quantity=1, discount=0)
+placeOrder("Headphones", 2); // Uses default discount (₹0)
+placeOrder("Smartphone", 3, 500); // Custom quantity and discount
+```
+
+---
+
+## Third Assignment: If-Else Statement
+
+```javascript
+let allStudents = ['A', 'B-', 1, 4, 5, 2]; // Grades taken from the given assignment 
+let studentsPassed = []; // This stores the passing students
+
+for (let i = 0; i < allStudents.length; i++) {
+    let grade = allStudents[i];
+
+    if (grade === 'A') {
+        studentsPassed.push(grade);
+    } else if (grade === 'A-') {
+        studentsPassed.push(grade);
+    } else if (grade === 'B') {
+        studentsPassed.push(grade);
+    } else if (grade === 'B-') {
+        studentsPassed.push(grade);
+    } else if (grade === 'C') {
+        studentsPassed.push(grade);
+    } else if (grade === 'C-') {
+        studentsPassed.push(grade);
+    } else if (grade >= 3) { 
+        studentsPassed.push(grade);
+    }
+}
+
+console.log(studentsPassed); // Output: ['A', 'B-', 4, 5]
+```
+
+---
+
+## Fourth Assignment: Looping Every 3rd Number Between 1-20
+
+```javascript
+for (let i = 1; i <= 20; i += 3) {
+    console.log(i);
+} // This prints every 3rd number from 1 to 20
+```
+
+