<html>

<head>

<script type="text/javascript">

/**=========================================**

 | 异步延时载入js/css文件

 | @example loadasync("http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js");

 | @author liuensong@gmail.com

 | @param string url js/css链接地址

 | @return 新生成element对象/null

 **=========================================**/

function loadasync(url){

    var elt=null, head=null, type=null;

    if(url){

        head = document.getElementsByTagName("head")[0];

        switch(url.split(".").pop()){

            case "css":

                elt = document.createElement("link");

                elt.rel = "stylesheet";

                elt.href = url;

                break;

            case "js":

                elt = document.createElement("script");

                elt.type = "text/javascript";

                elt.src = url;

                break;

            default:

                //something...

        }

        if(elt!=null && (typeof elt)=="object"){

            head.appendChild(elt);

        }

    }

    return elt;

}

/**=========================================**

 | 推断js/css文件是否已载入

 | @example isload("jquery.min.js");

 | @author liuensong@gmail.com

 | @param string fname js/css文件名称

 | @return bool true/false

 **=========================================**/

function isload(fname){

    var isload = false;

    var tags = {"js":"script", "css":"link"};

    var tagname = tags[fname.split(".").pop()];

    if(tagname != undefined){

        var elts = document.getElementsByTagName(tagname);

        for(i in elts){

            if((elts[i].href && elts[i].href.toString().indexOf(fname)!="-1") ||

                (elts[i].src && elts[i].src.toString().indexOf(fname)!="-1")){

                isload = true;

            }

        }

    }

    return isload;

}

//console.debug(loadasync("http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"));

//console.debug(isload("jquery.min.js"));

</script>

</head>

<body>

    <a href="javascript:;" onclick="loadasync('http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js');">loadasync</a>

    <a href="javascript:;" onclick="isload('jquery.min.js');">isload</a>

</body>

</html>