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 an auction system using the observer pattern.


You have two classes `Auctioneer` (*the person conducting the bid*) and `Bidder` (*the bidder bidding for the object*). 

Here's what the `Auctioneer` class needs to do:

* It should maintain a list of all bidders.

* It should have a function `registerBidder` to register the bidders.

* It should have an `announceNewBidderPrice` function to announce the bidding price given by a bidder.

* It should have a `notifyBidders` function to notify each bidder of a new bidding price.

`Bidder` should have the following:

* A `name` and `bidPrice`

* An `update` function that displays the `name` of the bidder along with the `bidPrice` they are giving. For example, `{insert name} is offering {insert bid price} dollars`. It should display `Sold to {insert name of bidder here}` if the bid price exceeds `500` dollars.

* A `giveNewPrice` function that sets the bid price of a bidder

## Input

The `announceNewBidderPrice` function is called after different bidders have given their prices

## Output

The name of the bidders and the prices they gave are displayed along with the name of the bidder who wins the bid

## Sample input

```
auctioneer = new Auctioneer();
bidder1 = new Bidder("Ross");
auctioneer.registerBidder(bidder1);
bidder2 = new Bidder("Joey");
auctioneer.registerBidder(bidder2);
bidder1.giveNewPrice(400);
bidder2.giveNewPrice(550);
auctioneer.announceNewBidderPrice()
```

## Sample output

```
"Ross is offering 400 dollars"
"Joey is offering 550 dollars"
"Sold to Joey"
```

# Problem statement

In this challenge, you have to implement an auction system using the observer pattern.


You have two classes `Auctioneer` (*the person conducting the bid*) and `Bidder` (*the bidder bidding for the object*). 

Here's what the `Auctioneer` class needs to do:

* It should maintain a list of all bidders.

* It should have a function `registerBidder` to register the bidders.

* It should have an `announceNewBidderPrice` function to announce the bidding price given by a bidder.

* It should have a `notifyBidders` function to notify each bidder of a new bidding price.

`Bidder` should have the following:

* A `name` and `bidPrice`

* An `update` function that displays the `name` of the bidder along with the `bidPrice` they are giving. For example, `{insert name} is offering {insert bid price} dollars`. It should display `Sold to {insert name of bidder here}` if the bid price exceeds `500` dollars.

* A `giveNewPrice` function that sets the bid price of a bidder

# Input

The `announceNewBidderPrice` function is called after different bidders have given their prices

# Output

The name of the bidders and the prices they gave are displayed along with the name of the bidder who wins the bid

# Sample input

```
auctioneer = new Auctioneer();
bidder1 = new Bidder("Ross");
auctioneer.registerBidder(bidder1);
bidder2 = new Bidder("Joey");
auctioneer.registerBidder(bidder2);
bidder1.giveNewPrice(400);
bidder2.giveNewPrice(550);
auctioneer.announceNewBidderPrice()
```

# Sample output

```
"Ross is offering 400 dollars"
"Joey is offering 550 dollars"
"Sold to Joey"
```

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


Before We Begin

Introduction To Design Patterns

Creational Patterns

Structural Patterns

Behavioral Patterns

Architectural Patterns

Conclusion

Challenge: Observer Pattern

Problem statement