SOURCE

<script>
        let Singleton = function(name){
            this.name = name;
            this.instance = null;
        };

        Singleton.prototype.getName =  function(){
            console.log(this.name)
        }

        Singleton.getInstance =  function(name){
            if(!this.instance){
                this.instance = new Singleton(name)
            }

            return this.instance;  
        }


       let a = Singleton.getInstance('ser1')
       console.log('a',a)

</script>