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 need to implement the visitor pattern to separate `Rock` music from the other genres of music by creating a separate playlist. You need to implement the `RockMusicVisitor` class for this purpose. As you can see, it contains the `visit` method, which should return the rock music playlist.

>**Note:** the rock music playlist only needs to contain the names of the songs, not the entire `Song` object.

Next, you need to implement a `Song` class. A `Song` object will have the following properties: `name` and `genre`. You also need to define the two functions: `getName` and `getGenre`.

Finally, you need to implement the `MusicLibrary` class. It should store a list of all the songs, regardless of the genres. You need to implement the `addSong` function to add a song and `accept` function to allow the `RockMusicVisitor` to visit the music library.  

## Input

The `accept` function is called with `RockMusicVisitor` as a parameter


## Output

A playlist containing names of all the rock songs from the library is returned


## Sample input

```
var rockMusicVisitor = new RockMusicVisitor()
var song1 = new Song("Bohemian Rhapsody","Rock")
var song2 = new Song("Stairway to Heaven","Rock")
var song3 = new Song("Oops I did it again", "Pop")
var song4 = new Song("Crazy", "Country")
var musicLibrary = new MusicLibrary()
musicLibrary.addSong(song1)
musicLibrary.addSong(song2)
musicLibrary.addSong(song3)
musicLibrary.addSong(song4)
console.log(musicLibrary.accept(rockMusicVisitor))
```
## Sample output

```
["Bohemian Rhapsody","Stairway to Heaven"]
```

# Problem statement

In this challenge, you need to implement the visitor pattern to separate `Rock` music from the other genres of music by creating a separate playlist. You need to implement the `RockMusicVisitor` class for this purpose. As you can see, it contains the `visit` method, which should return the rock music playlist.

>**Note:** the rock music playlist only needs to contain the names of the songs, not the entire `Song` object.

Next, you need to implement a `Song` class. A `Song` object will have the following properties: `name` and `genre`. You also need to define the two functions: `getName` and `getGenre`.

Finally, you need to implement the `MusicLibrary` class. It should store a list of all the songs, regardless of the genres. You need to implement the `addSong` function to add a song and `accept` function to allow the `RockMusicVisitor` to visit the music library.  

# Input

The `accept` function is called with `RockMusicVisitor` as a parameter


# Output

A playlist containing names of all the rock songs from the library is returned


# Sample input

```
var rockMusicVisitor = new RockMusicVisitor()
var song1 = new Song("Bohemian Rhapsody","Rock")
var song2 = new Song("Stairway to Heaven","Rock")
var song3 = new Song("Oops I did it again", "Pop")
var song4 = new Song("Crazy", "Country")
var musicLibrary = new MusicLibrary()
musicLibrary.addSong(song1)
musicLibrary.addSong(song2)
musicLibrary.addSong(song3)
musicLibrary.addSong(song4)
console.log(musicLibrary.accept(rockMusicVisitor))
```
# Sample output

```
["Bohemian Rhapsody","Stairway to Heaven"]
```

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

Before We Begin

Introduction To Design Patterns

Creational Patterns

Structural Patterns

Behavioral Patterns

Architectural Patterns

Conclusion

Challenge: Visitor Pattern

Problem statement