单例模式

var createSingleInstance = function() {
       var instance = null;
       return function(fn) {
           if (!instance) {
               instance = new fn();
           }
           return instance;
       }
   }();

   function createModal(){
       this.name = 1;
   }
   var fnA = createSingleInstance(createModal);
   var fnB = createSingleInstance(createModal);
   console.log(fnA === fnB);

var getSingle = function (fn) {
       var result;
       return function () {
           return result || ( result = fn.apply(this, arguments) );
       }
   };