判断是否已经引入js

//判断是否已经引入js        function isInclude(name){            var js= /js$/i.test(name);            var es=document.getElementsByTagName(js?'script':'link');            for(var i=0;i<es.length;i++)                if(es[i][js?'src':'href'].indexOf(name)!=-1)return true;            return false;        }

if (!isInclude("swiper.js")) {                    var oHead = document.getElementsByTagName('HEAD').item(0);                    var oScript = document.createElement("script");                    oScript.type = "text/javascript";                    oScript.src = "js/swiper.js";}