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

class Auctioneer
{
    constructor(){
        this.bidderList = []
    }
    
    announceNewBidderPrice()
    {
        this.notifyBidders();
    }
     
    registerBidder(bidder)
    {
        this.bidderList.push(bidder);
    }
    
    notifyBidders()
    {
        this.bidderList.forEach(bidder => bidder.update())
    }
}


class Bidder 
{
    constructor(name){
        this.name = name
        this.bidPrice = null
    }
    
    update()
    {
        console.log(`${this.name} is offering ${this.bidPrice} dollars`);
        if (this.bidPrice > 500)
        {
            console.log(`Sold to ${this.name}`);
        }
    }
        
    giveNewPrice(price)
    {
        this.bidPrice = price;
    }
}

auctioner = new Auctioneer();
bidder1 = new Bidder("Ross");
auctioner.registerBidder(bidder1);
bidder2 = new Bidder("Joey");
auctioner.registerBidder(bidder2);
bidder1.giveNewPrice(200);
bidder2.giveNewPrice(350);
auctioner.announceNewBidderPrice()
bidder1.giveNewPrice(400);
bidder2.giveNewPrice(550);
auctioner.announceNewBidderPrice()

# Explanation

In this example, we have the subject class `Auctioneer` that stores the list of all bidders to whom it announces the bidding prices. 

```
class Auctioneer
{
    constructor(){
        this.bidderList = []
    }
    //code...
}
```

The `constructor` initializes the list `bidderList` that stores all the bidders participating in the auction. 

It also defines the `registerBidder` function that registers a bidder for the auction.

```
registerBidder(bidder)
{
        this.bidderList.push(bidder);
}
```


It also has the `announceNewBidderPrice` function:

```
announceNewBidderPrice()
{
   this.notifyBidders();
}
```



When a bidder gives a price for the object being auctioned, the auctioneer invokes the `announceNewBidderPrice` function to notify all the bidders about the price. How are the bidders notified?  They’re notified using the  `notifyBidders` function.

```
notifyBidders()
{
   this.bidderList.forEach(bidder => bidder.update())
}
```

This function sends an announcement regarding the price given by each bidder in the list. It does so by calling the `update` function. We'll take a look at it when we discuss the `Bidder` class.

Here's what the `Bidder` class looks like:

```
class Bidder 
{
  constructor(name){
     this.name = name
     this.bidPrice = null
   }
   //code... 
}
```

The `constructor` initializes the properties `name` and `bidPrice` for a bidder. 

The `bidPrice` is set using the `giveNewPrice` function:

```
giveNewPrice(price)
{
   this.bidPrice = price;
}

```

The `Bidder` also has the update function.

```
update(){
   console.log(`${this.name} is offering ${this.bidPrice} dollars`);
    if (this.bidPrice > 500){
            console.log(`Sold to ${this.name}`);
  }
}
```
This function is invoked by the `Auctioneer` to notify the bidders about the new price given by a bidder. Hence, it displays a message announcing the `name` of the bidder and the `bidPrice` offered by them. It also checks if the bidder's price is greater than `500`. If it is, the object is sold to that bidder, and an announcement of the winner is made.  





# Explanation

In this example, we have the subject class `Auctioneer` that stores the list of all bidders to whom it announces the bidding prices. 

```
class Auctioneer
{
    constructor(){
        this.bidderList = []
    }
    //code...
}
```

The `constructor` initializes the list `bidderList` that stores all the bidders participating in the auction. 

It also defines the `registerBidder` function that registers a bidder for the auction.

```
registerBidder(bidder)
{
        this.bidderList.push(bidder);
}
```


It also has the `announceNewBidderPrice` function:

```
announceNewBidderPrice()
{
   this.notifyBidders();
}
```



When a bidder gives a price for the object being auctioned, the auctioneer invokes the `announceNewBidderPrice` function to notify all the bidders about the price. How are the bidders notified?  They’re notified using the  `notifyBidders` function.

```
notifyBidders()
{
   this.bidderList.forEach(bidder => bidder.update())
}
```

This function sends an announcement regarding the price given by each bidder in the list. It does so by calling the `update` function. We'll take a look at it when we discuss the `Bidder` class.

Here's what the `Bidder` class looks like:

```
class Bidder 
{
  constructor(name){
     this.name = name
     this.bidPrice = null
   }
   //code... 
}
```

The `constructor` initializes the properties `name` and `bidPrice` for a bidder. 

The `bidPrice` is set using the `giveNewPrice` function:

```
giveNewPrice(price)
{
   this.bidPrice = price;
}

```

The `Bidder` also has the update function.

```
update(){
   console.log(`＄{this.name} is offering ＄{this.bidPrice} dollars`);
    if (this.bidPrice > 500){
            console.log(`Sold to ＄{this.name}`);
  }
}
```
This function is invoked by the `Auctioneer` to notify the bidders about the new price given by a bidder. Hence, it displays a message announcing the `name` of the bidder and the `bidPrice` offered by them. It also checks if the bidder's price is greater than `500`. If it is, the object is sold to that bidder, and an announcement of the winner is made.  





This lesson will explain the solution to the problem from the previous coding challenge.


Before We Begin

Introduction To Design Patterns

Creational Patterns

Structural Patterns

Behavioral Patterns

Architectural Patterns

Conclusion

Challenge: Solution Review

Solution #