单例模式

var CreateDiv = function (html) {
    this.html  = html;
    this.init();
};

CreateDiv.prototype.init = function () {
    var div = document.createElement('div');
    div.innerHTML = this.html;
    document.body.appendChild(div);
};

var ProxySingletonCreateDiv = (function () {
   var instance = null ;
   return function (html) {
       if(!instance){
           instance = new CreateDiv(html)
       }
       return instance
   }
})();

var a = new ProxySingletonCreateDiv("seven1") ;
console.log(a);
var b = new ProxySingletonCreateDiv("seven2") ;
console.log(b);