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 configuration that uses the singleton pattern. You are given a class `ConfigureVals`. Define it as follows:

* It should have a `constructor` that defines the properties `xpoint`, `ypoint`, and `shape`.

* The `constructor` should initialize `xpoint`, `ypoint`, and `shape` to `0`, `0`, and `null` if the values for these properties are not passed to the `constructor`.

* Only a single instance of the class can be made by defining the function `getConfiguration`.

## Input

The `getConfiguration` method invoked

## Output

The instance created after the `getConfiguration` function is invoked

## Sample input

```
getConfiguration({ xpoint: 8, ypoint : 9, shape : rectangle }); //first call

getConfiguration({ xpoint : 2, ypoint : 4, shape : circle }); //second call

```

## Sample output

```
ConfigureVals { xpoint: 8, ypoint: 9, shape: 'rectangle' }

ConfigureVals { xpoint: 8, ypoint: 9, shape: 'rectangle' }
```

# Problem statement

In this challenge, you have to implement a configuration that uses the singleton pattern. You are given a class `ConfigureVals`. Define it as follows:

* It should have a `constructor` that defines the properties `xpoint`, `ypoint`, and `shape`.

* The `constructor` should initialize `xpoint`, `ypoint`, and `shape` to `0`, `0`, and `null` if the values for these properties are not passed to the `constructor`.

* Only a single instance of the class can be made by defining the function `getConfiguration`.

# Input

The `getConfiguration` method invoked

# Output

The instance created after the `getConfiguration` function is invoked

# Sample input

```
getConfiguration({ xpoint: 8, ypoint : 9, shape : rectangle }); //first call

getConfiguration({ xpoint : 2, ypoint : 4, shape : circle }); //second call

```

# Sample output

```
ConfigureVals { xpoint: 8, ypoint: 9, shape: 'rectangle' }

ConfigureVals { xpoint: 8, ypoint: 9, shape: 'rectangle' }
```

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

Before We Begin

Introduction To Design Patterns

Creational Patterns

Structural Patterns

Behavioral Patterns

Architectural Patterns

Conclusion

Challenge: Singleton Pattern

Problem statement