Use Case of Singleton Method Design Pattern in JavaScript

There is a application of singleton pattern like cache-memory, database connection, drivers, logging. Some major of them are :-

• Hardware interface access: Singleton classes are also used to prevent concurrent access of class. Practically singleton can be used in case external hardware resource usage limitation required e.g. Hardware printers where the print spooler can be made a singleton to avoid multiple concurrent accesses and creating deadlock.
• Logger : Singleton classes are used in log file generations. Log files are created by the logger class object.
  • Suppose an application where the logging utility has to produce one log file based on the messages received from the users.
  • If there is multiple client application using this logging utility class they might create multiple instances of this class and it can potentially cause issues during concurrent access to the same logger file.
• Configuration File: This is another potential candidate for Singleton pattern because this has a performance benefit as it prevents multiple users to repeatedly access and read the configuration file or properties file. It creates a single instance of the configuration file which can be accessed by multiple calls concurrently as it will provide static config data loaded into in-memory objects.
• Cache: We can use the cache as a singleton object as it can have a global point of reference and for all future calls to the cache object the client application will use the in-memory object.

Singleton Method or Singleton Design Pattern is a part of the Gang of Four design pattern and it is categorized under creational design patterns. It is one of the most simple design patterns in terms of modeling but on the other hand, this is one of the most controversial patterns in terms of complexity of usage.