JavaScript Singleton Design Patterns

What is SingleTon Pattern?

The Singleton Pattern is a design pattern that ensures a class has only one instance and provides a global point of access to it.
This single instance is unmodifiable.

It can be accessed globally throughout the application

This singleton can be shared globally across multiple files within the application. The imports of this Singleton all reference the same instance

class Singleton {
    constructor() {
        this.data = [];
    }
    
    addData(item) {
        this.data.push(item);
    }

    getData() {
        return this.data;
    }
}

const instance = new Singleton();
Object.freeze(instance); // Prevent modification

export default instance;

Now, If you import Singleton file into multiple files, you always get the same instance.

Where to use:

When you have objects that need to coordinate actions across an application, like a database connection pool

When you want to maintain a single configuration object that’s accessible across different modules.

When you need a global logging service that any part of the application can access.

Conclusion

Singleton Pattern is powerful, but it should be used judiciously, as it creates global state and can make testing challenging. When used in the right context, however, it can help you organize and simplify the structure of your application.

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