学步园

动态加载脚本文件一般来说有两种方法，一种是动态创建SCRIPT元素，一种是使用XMLHTTP访问后进行eval，这里我重点介绍前者，前者的兼容

//
// Copyright(C) 2006 Forbes Pu. All right reserved.
//
var BROWSER_IE = window.navigator.userAgent.indexOf("MSIE") != -1;
var SCRIPT_TIMEOUT = 20000;

function $import(jsurl, fCallback, fError){
    
    if (typeof(fCallback) != "function") fCallback = new Function();
    if (typeof(fError) != "function") fError = new Function();

    var oScriptEl, oTimeoutHDL, oHead;
    oScriptEl = document.createElement("script");
    oScriptEl.type = "text/javascript";
    oScriptEl.language = "javascript";
    oScriptEl.src = jsurl;
    oScriptEl.onreadystatechange = doCallback;
    
    if (BROWSER_IE){
        oScriptEl.onload = function(){
            this.readyState = "complete";
            doCallback();
        };
    };
    
    oTimeoutHDL = window.setTimeout(doError, SCRIPT_TIMEOUT);
    document.getElementsByTagName("head")[0].appendChild(oScriptEl);

    function doCallback(){
        if (oScriptEl.readyState == "complete" || oScriptEl.readyState == "loaded"){
            oScriptEl.onload = oScriptEl.onreadystatechange = new Function();
            fCallback();
            window.clearTimeout(oTimeoutHDL);
            oScriptEl.parentNode.removeChild(oScriptEl);
        }
    };

    function doError(){
        oScriptEl.parentNode.removeChild(oScriptEl);
    };
};

在IE环境下SCRIPT元素的onreadystatechange事件可以作回调检查是否已经加载完毕，在非IE环境下对元素的onload事件来判断是否已加载。