一、代码示例：

 

<html>
<head> 
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
<title>动态加载JS文件</title>
</head>
<body>
<button id="btn" onclick="loanScript('test.js'),callback">加载js文件</button>    
<script type="text/javascript">

    function callback(){
        console.log("script load complete");
        loadSuccess();
    }
    function loanScript(url,callbackFun){
        var script = document.createElement("script");
        script.type = "text/javascript";
        //兼容IE浏览器
        if(script.readyState){
            script.onreadystatechange = function(){
                if(script.readyState == "loaded" || script.readyState == "complete"){
                    script.onreadystatechange = null;
                    callbackFun();
                }
            }
        }else{//其他浏览器
            script.onload = function(){
                callbackFun();
            };

        }

        script.src = url;
        document.getElementsByTagName("head")[0].appendChild(script);
    }
</script>
</body>
</html>

 

注意除了Firefox和Opera保证脚本文件按照代码顺序加载，其他浏览器不保证文件按照你指定的顺序加载，可通过串联操作保证文件的加载次序代码如下

 

window.onload=function(){
    loadScript("file1.js",function(){
        loadScript("file2.js",function(){
            loadScript("file3.js",function(){
                alert("all js document are loaded");
            });
        });
    });

}