The ultimate guide to coding interviews: Learn and practice JavaScript design patterns tested by FAANG engineers. Get interview-ready in just a few hours with battle-tested solutions.

If you're an experienced developer, chances are your interviewer won't ask you about language syntax. Instead, they'll focus on things that test your understanding of software architecture, and how capable you are at finding optimized solutions to given problems. 

That’s where a strong understanding of design patterns comes in handy. It's often useful to be able to draw on established patterns instead of reinventing the wheel.

In this course, you will learn how to effectively deploy design patterns to answer interview questions. The course is divided into four sections: Creational Patterns, Structural Patterns, Behavioral Patterns, and Architectural Patterns. Each section has its own set of design patterns which you’ll learn to use through various challenges. 

Every challenge contains a detailed solution explanation. By the end of this course (and with some practice), you will be able to confidently use design patterns to tackle advanced coding interview questions in JavaScript.

JavaScript Design Patterns for Coding Interviews

# Problem statement

In this challenge, you have to implement the MVC pattern to display the items in a shopping cart.

You have three components:

* `ShoppingCartModel`

  The shopping cart model should have the following properties: `itemNumber`, `itemName`, `itemQuantity`, and `itemPrice`. It should also have a **get** function for each property.  

* `ShoppingCartView`

   You are already given the part of the code that initializes the current view for the `controller` and the `displayItem` function that displays an item's information. 

  Your task is to implement a `buyItem` function to buy an item. 

  A `changeItemQuantity` function that updates the quantity of an item in the cart. It should take the following parameters: `itemNumber` and `newQuantity`.

* `ShoppingCartController`
  
   The controller should update the view whenever a change occurs in the shopping cart model or if a user edits the view.

   
# Input

The `buyItem` function is called to buy items and `changeItemQuantity` is called to change the quantity of an existing item


# Output

The items in the cart are displayed


# Sample input

```
var view = new ShoppingCartView();
var controller = new ShoppingCartController();
view.registerWith(controller);
view.buyItem("Popcorn", 3, 2.50);
view.changeItemQuantity(0,6);
```

# Sample output

```
"Item Number: 0"
"Item: Popcorn"
"Quantity: 3"
"Price: 2.5"
"Item Number: 0"
"Item: Popcorn"
"Quantity: 6"
"Price: 2.5"
```

In this challenge, you have to implement the MVC pattern to solve the given problem.

Before We Begin

Introduction To Design Patterns

Creational Patterns

Structural Patterns

Behavioral Patterns

Architectural Patterns

Conclusion

Challenge: MVC Pattern

Problem statement