动态添加脚本，并触发回调函数 初步实现按需加载

 

 function loadScript(url, callback){

    var script = document.createElement("script")

    script.type = "text/javascript";

    if (script.readyState){  //IE

        script.onreadystatechange = function(){

            if (script.readyState == "loaded" ||

                    script.readyState == "complete"){

                script.onreadystatechange = null;

                callback();

            }

        };

    } else {  //Others

        script.onload = function(){

            callback();

        };

    }

    script.src = url;

    document.getElementsByTagName("head")[0].appendChild(script);

}

 

调用方法：

 

 

loadScript("http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js", function(){

	alert('load success1!');

});