JS添加验证页面中script标签中是否存在jquery文件

 1 window.onload = function()
 2 {
 3 var al = document.getElementsByTagName("script");
 4 var new_element=document.createElement("script"); 
 5 var joine = []
 6 for(var i = 0; i<al.length; i++)
 7 {
 8     joine.push(al[i].getAttribute("src"));
 9 }
10 var ajoine = joine.join(",");
11 console.log(ajoine);
12 if(IndexDemo(ajoine,‘jquery.min.js‘)>0)
13     {
14         console.log(‘1‘);
15         //alert(1);
16     }else{
17         console.log(‘2‘);
18         var new_element=document.createElement("script"); 
19         new_element.setAttribute("type","text/javascript"); 
20         new_element.setAttribute("src","/static/js/jquery-1.5.1/jquery.min.js");// 在这里引入了a.js 
21         document.body.appendChild(new_element); 
22         //alert(2);
23     }
24 }
25 
26 function IndexDemo(str1,str2){
27    var list = str1
28    var s = list.indexOf(str2);
29    return(s);
30 }