SOURCE

var Singleton = function( name ){
 console.log(name) 
 this.name = name; 
 this.instance = null; 
}; 
Singleton.prototype.getName = function(){ 
 alert ( this.name ); 
}; 
Singleton.getInstance = function( name ){ 
 if ( !this.instance ){ 
 this.instance = new Singleton( name ); 
 } 
 return this.instance; 
}; 
var a = Singleton.getInstance( 'sven1' ); 
var b = Singleton.getInstance( 'sven2' ); 
console.log ( a === b ); // true