Singleton Design Pattern
What is 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.
- This is how we can use singleton in javascript.
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