Five (5) JavaScript Design Patterns for Efficient Development

Among the numerous design patterns available, this guide will focus on five of the most commonly used. These patterns have been selected for their practicality and ease of adoption, ensuring you can begin applying them to real-world scenarios immediately.

What are Design Patterns?

Design patterns are widely recognized solutions to common and complex problems encountered in object-oriented programming. Rather than being rigid or hard-coded, these patterns provide flexible, adaptable frameworks that can be applied effectively when their underlying principles are well understood.

For many, grasping the nuanced nature of these solutions—or identifying when and where to apply them—can be challenging. This article aims to simplify these concepts by explaining their practical applications, helping you make more informed decisions in your projects.

Factory Pattern

The goal of the factory pattern is to create objects that can be modified later. Below is an example of a factory Method that we can use to create different kinds of furniture.

In this example, we define new classes with constructors that include the desired attributes for the object. By creating a new instance of the class, we can pass in parameters corresponding to the attributes we’ve set (e.g., name and legs).

Use Cases: This approach is particularly useful when you need to create multiple objects with the same set of attributes. For instance, it can be applied when adding entries to a table or registering new users on a website. Additionally, a factory can be used to integrate data from various database tables, streamlining the object creation process.
While this method is already quite powerful, we can enhance its utility further by introducing abstraction. For example, we can create a factory that manages other factories, making the process even more efficient and scalable. The example below demonstrates how to implement this advanced pattern.

By introducing a parent furniture factory to manage smaller, specialized factories, we can streamline the process of creating different types of furniture. Instead of manually interacting with individual factories, we simply specify the type of furniture we want, and the parent factory takes care of the rest. This approach, often referred to as a “factory stack,” significantly simplifies development and enhances the reusability of our code.

Use Cases: This advanced factory pattern expands upon the capabilities of a traditional factory. Beyond creating individual objects, it shines in scenarios such as unit testing, where it can generate mock data efficiently. It is also particularly useful for constructing complex objects containing arrays or nested objects—like cars with a list of makes and models or warehouse employees with varying work schedule data. The flexibility and scalability of this pattern make it an invaluable tool in numerous applications.

 

Adapter Pattern

Sometimes we have objects that are incompatible with each other, but we need them to interact for our purposes.

In this example, we work with an array of cities and a function designed to determine which city has the largest population. However, the population data in our dataset is not in the correct format. To resolve this, we use an adapter function called toMillionsAdapter to transform the data into the expected format.

Use Cases: One common scenario for using the Adapter Pattern is when integrating with external APIs. For instance, suppose one API returns data in JSON format, but another API that needs to process or store this information only accepts XML. Since the two APIs have incompatible data formats or interfaces, the adapter bridges the gap by transforming the data as needed.
This pattern is particularly valuable for companies that rely on external APIs to enhance their operations, ensuring smooth communication and compatibility between different systems.

 

Decorator Pattern

The Decorator Pattern enhances the reusability of your existing code by introducing a “wrapper” around an existing function. This wrapper allows you to extend or modify the function’s behavior for specific use cases without altering its original implementation. Since the wrapped function’s core functionality remains intact, this approach minimizes the need for extensive retesting and reduces the amount of new code you need to write.
By applying the decorator pattern, you can incrementally add features while maintaining clean, modular, and testable code. This makes it a powerful tool for managing evolving requirements in a scalable and maintainable way.

The logMessage function is a simple utility that takes a message, such as “Hello, world!”, and logs it to the console. This function is essential, and its core functionality should remain unchanged. However, in certain use cases, such as logging messages with a timestamp, we need to extend its behavior without modifying its original implementation.

To achieve this, we can create a decorator function called timestampDecorator. This decorator accepts any function as a parameter and enhances it by adding additional functionality—specifically, logging a timestamp along with the original message.

Results:

Use Cases: I have used this decorator pattern to add styling to dynamically generated HTML elements or components that wrap other elements. For example, a parent component can manage styling and data management, while the child components determine how the data is displayed—such as tables or charts. This allows for greater modularity and interchangeability, ensuring that styles and functionality are applied consistently across different components.
This pattern is also beneficial on the backend, where it can be used for sorting procedures or in combination with other design patterns to enhance functionality.
 

Singleton pattern

Singleton is a design pattern used to ensure that a class has only one instance and provides a global point of access to that instance. There are certain classes in applications that should never be changed, such as critical constants used for calculations or essential values like min/max limits for users. The Singleton pattern makes sure that such objects cannot be copied, modified, or duplicated.
This ensures that the single instance of the class maintains its integrity and consistency across different parts of the application.

Lets say you had a very important key, that could crash the application if it was ever altered.

Using Object.freeze() on our importantKey is a strong way to make the contents of our object immutable. Here is another example to safeguard just a number. My IntelliSense is already warning me that I cannot change ‘value’.

Use Cases: The Singleton pattern is widely used at the base level of many applications to safeguard important objects, such as configurations or special keys, ensuring they remain immutable. This approach is essential whenever critical data needs to be maintained as a single, unchangeable instance across various parts of the application.
 

Observer pattern

The Observer Pattern is used to establish a one-to-many dependency between objects, meaning when one object (the “subject”) changes, all dependent objects (the “observers”) are notified and updated accordingly.

Imagine a news application where users subscribe to receive updates about certain topics. Whenever new information becomes available, all subscribers are notified. Similarly, in coding, this pattern is used to manage situations where multiple components or parts of an application need to respond to specific events or changes, such as when data is updated, a button is clicked, or a state changes. This ensures that all relevant components stay in sync with the changes occurring in the application.

The Subject in the Observer Pattern manages and tracks its observers. It allows us to subscribe and unsubscribe observers to ensure they receive updates when changes occur. Additionally, the Subject can notify all subscribed observers, who then perform their own actions based on the information provided. This ensures that all relevant components are synchronized and react appropriately to any updates or events.

Here our subscriber class will log a string when the subject.notify() method is called.

A subject (publisher) is created to manage its observers. Observers can be subscribed to receive updates whenever the subject changes. Once subscribed, the subject notifies all observers with new data through its notify method. Each observer handles this data independently, performing actions based on the updates they receive.

Additionally, subscribers can be unsubscribed from the subject, ensuring they no longer receive updates. This allows for a flexible relationship between the subject and its observers, maintaining control over who is notified of changes.

Use Cases: I have used the Observer Pattern to create subjects in global services, helping to avoid issues with traversing complex component hierarchies. This makes it easier to update variables between parent and child components, especially useful when changes need to be made across multiple forms simultaneously or when preparing data for backend submission.

Utilizing promises in conjunction with this pattern provides significant flexibility in component communication and reduces unnecessary API calls, streamlining overall processes.

However, nesting observer patterns within themselves is not recommended, as it can lead to increased testing complexity and a significant rise in code complications.

Conclusion

These five design patterns are foundational to most JavaScript web applications. By understanding and implementing these patterns, developers can enhance productivity, improve code reusability, and streamline testing processes, resulting in more maintainable and efficient solutions.

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