js代码封装

    <script type="text/javascript">    var calculator=(function(){       var add=function(v1,v2){        return v1+v2;       }       var substract=function(v1,v2){            return v1-v2;       }        var mutiply=function(v1,v2){            return v1*v2;       }       var divide=function(v1,v2){         return v1/v2;       }       return {            add:add,            substract:substract,            mutiply:mutiply,            divide:divide       }    })();    </script>    <script>       //开闭原则 对直接修改关闭、扩展开放        var calculator=(function(cal){        cal.mod=function(v1,v2){          return v1%v2;        }        return cal;     })(window.calculator||{})    </script>