Singleton Design Pattern - Javascript

Singleton Design Pattern

• Singleton design pattern is one of the creational design patterns.
• Singleton design pattern describes how the object should be created.
• It ensures that the class has only one instance and provides a global access point to that instance.
• Singleton design pattern is discovered because of bugs due to multiple instances where only one instance should be present.

When to use Singleton Design Pattern

• We need to ensure only one instance of the class is present.
• We need to provide a global access point to a class instance.

Code example

• A logger is one of the real-world use cases in which we want to have a single instance globally.

let instance = null;

class Logger {
    constructor(logger_name) {
        if (!instance) {
            this.name = logger_name;
            instance = this;
        } else {
            return instance;
        }
    }
}

const logger_1 = new Logger('Logger1');
const logger_2 = new Logger('Logger2');

console.log(logger_1); // Logger {name: 'Logger1'}
console.log(logger_2); // Logger {name: 'Logger1'}

• In this example, you can see that even if we try to create 2 different instances of the Logger class there will be only one instance of the Logger class.
• You can find the code in the GitHub repository .

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