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 a *directory system* using the composite pattern. 

You have been given the following skeleton code:

class Directory{
    constructor(name,lastModified,size){
        this.name = name
        this.lastModified = lastModified
        this.size = size
    }
    getLastmodified(){}
    getSize(){}
    getName(){}
}


class File extends Directory{
}

class Folder extends Directory{
}

It's up to you to figure out which class will be the component, leaf subclass, and composite subclass.

A `Directory` has the following properties:

* `name`: the name of the file/folder

* `lastModified`: the time in *minutes* since the last modification

* `size`: the size of the file/folder in *kilobytes*

You have the following functions in the `Directory` class:

* `getLastmodified`: Returns the `lastModified` time of a file. In the case of a folder with multiple files, it should return the *minimum* of the `lastmodified` times of all files. 

* `getSize`: Returns the `size` of a file/folder.

* `getName`: Returns the `name` of the file or all the files in the case of a folder.

The composite subclass should contain the following additional functions as well:

* `addFile`

* `removeFile`



## Input

Calling the given functions on files and folders

## Output

The correct output after calling these functions such as `lastModified` time, `name`, and `size`

## Sample input

```
const file = new File("penguiny.png",6,12)
file.getLastmodified()
file.getName()
file.getSize()
```

## Sample output

```
6
"penguiny.png"
12
```

# Problem statement

In this challenge, you have to implement a *directory system* using the composite pattern. 

You have been given the following skeleton code:

It's up to you to figure out which class will be the component, leaf subclass, and composite subclass.

A `Directory` has the following properties:

* `name`: the name of the file/folder

* `lastModified`: the time in *minutes* since the last modification

* `size`: the size of the file/folder in *kilobytes*

You have the following functions in the `Directory` class:

* `getLastmodified`: Returns the `lastModified` time of a file. In the case of a folder with multiple files, it should return the *minimum* of the `lastmodified` times of all files. 

* `getSize`: Returns the `size` of a file/folder.

* `getName`: Returns the `name` of the file or all the files in the case of a folder.

The composite subclass should contain the following additional functions as well:

* `addFile`

* `removeFile`



# Input

Calling the given functions on files and folders

# Output

The correct output after calling these functions such as `lastModified` time, `name`, and `size`

# Sample input

```
const file = new File("penguiny.png",6,12)
file.getLastmodified()
file.getName()
file.getSize()
```

# Sample output

```
6
"penguiny.png"
12
```

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

Before We Begin

Introduction To Design Patterns

Creational Patterns

Structural Patterns

Behavioral Patterns

Architectural Patterns

Conclusion

Challenge: Composite Pattern

Problem statement