The Singleton pattern ensures that a class has only one instance and provides a global point of access to it. It encapsulates "just-in-time initialization" or "initialization on first use." This pattern is useful when exactly one object is needed to coordinate actions across the system. The document provides examples of implementing the Singleton pattern in C# and JavaScript, including lazy instantiation that only creates the instance when first accessed.

1. Singleton Pattern Lim Borey Yoolk Inc.

5. Implementation in JavaScript Singleton = (function() { var privateAttribute1 = false; var privateAttribute2 = [1, 2, 3]; return { publicAttribute1: true, publicAttribute2: 10, publicMethod1: function() { ... }, publicMethod2: function(args) { ... } }; })();

6. Lazy Instantiate Singleton Singleton = (function() { varuniqueInstance; // Private attribute that holds the single instance. function constructor() { // All of the normal singleton code goes here. return{ greeting : function() { alert("hello"); } } } return { getInstance: function() { if(!uniqueInstance) { // Instantiate only if the instance doesn't exist. uniqueInstance = constructor(); } return uniqueInstance; } } })(); Singleton.getInstance().greeting();

7. References Singleton pattern (2010, Feb 08), http://en.wikipedia.org/wiki/Singleton_pattern Erich G., Richard H., Ralph J., John M. V., 1995, Design Patterns: Elements of Reusable Object-Oriented Software, Addison-Wesley Professional Ross H., Dustin D. , 2007, Pro JavaScript™ Design Patterns, Apress