JavaScript Creational Design Patterns Singleton Pattern
Example
The Singleton pattern is a design pattern that restricts the instantiation of a class to one object. After the first object is created, it will return the reference to the same one whenever called for an object.
var Singleton = (function () {
// instance stores a reference to the Singleton
var instance;
function createInstance() {
// private variables and methods
var _privateVariable = 'I am a private variable';
function _privateMethod() {
console.log('I am a private method');
}
return {
// public methods and variables
publicMethod: function() {
console.log('I am a public method');
},
publicVariable: 'I am a public variable'
};
}
return {
// Get the Singleton instance if it exists
// or create one if doesn't
getInstance: function () {
if (!instance) {
instance = createInstance();
}
return instance;
}
};
})();
Usage:
// there is no existing instance of Singleton, so it will create one
var instance1 = Singleton.getInstance();
// there is an instance of Singleton, so it will return the reference to this one
var instance2 = Singleton.getInstance();
console.log(instance1 === instance2); // true
