JS工具类——Js动态加载类

function JsLoader(){};
JsLoader.loaded = [];
JsLoader.prototype = {
    _path : null,//要加载的JS的路径
    _head : null,//文档对象的head头对象
    /**
     * 主要调用方法.
     */
    require : function(jsPath,callback) {
        if(!this._check(jsPath))return false;
        if(this._isload(jsPath))return true;
        this._ajaxLoad(callback);
        return true;
    },
    load : function(jsPath,callback) {
        return this.require(jsPath, callback);
    },
    _check : function(jsPath) {
        if(!jsPath) {
            alert('请指定要加载的JS路径！');
            return false;
        }
        var head = document.getElementsByTagName('head');
        if(!head||head.length<1) {
            alert('文档对象document必须有HEAD头！');
            return false;
        }
        this._path = jsPath;
        this._head = head[0];
        return true;
    },
    _isload : function(jsPath) {
        for(var i=0; i<JsLoader.loaded.length; i++) {
            if(JsLoader.loaded[i].toLowerCase()==jsPath.toLowerCase())
            return true;
        }
        JsLoader.loaded[JsLoader.loaded.length]=jsPath;
        return false;
    },
    _ajaxLoad : function(callback) {
        var head = this._head;
        base.request(this._path,function(xmlHttp, error) {
            var script = document.createElement('script');
            script.type = "text/javascript";
            script.text = xmlHttp.responseText;
            head.appendChild(script);
            if(!callback)return;
            try{
                if(typeof(callback)=='function')  callback();
                else eval(callback);
            }catch(ex){alert(ex.message);};
        });
    }
};