- [Design Pattern](#pattern)

<a name=“pattern”/>

- [Singleton Pattern](#singleton)

<a name=“singleton”/>

The singleton design pattern restricts the instantiation of a function/class to one variable/object.

Uses:

1. When exactly one variable/object is needed to coordinate actions across the system.

2. Reduce the need of global variables.

3. The getInstance method demonstates another design pattern called Lazy Load.

``` javascript

var Singleton = (function () {

var instance;

function createInstance() {

var object = new Object("I am the instance");

return object;

}

return {

getInstance: function () {

if (!instance) {

instance = createInstance();

}

return instance;

}

};

})();

function run() {

var instance1 = Singleton.getInstance();

var instance2 = Singleton.getInstance();

alert("Same instance? " + (instance1 === instance2)); //Output: Same instance? true

}

Ref: