class Single{
     private static instance:Single;
     public static getInstance():Single{
            if(this.instance == null){
                    this.instance = new Single();
            }
            return this.instance;
     }
     public run(){

     }
}

Single.getInstance().run();

class BaseClass {
    public static getInstance():any {
        var Class:any = this;
        if (!Class._instance) {
                Class._instance = new Class();
        }
        return Class._instance;
    }
}

class Single extends BaseClass{
        public run(){
        }
}

Single.getInstance().run();