//加载新的js  
    function _GetJsData(url, callback) {  
        var scripts = document.createElement("script");  
        document.body.appendChild(scripts);  
      
        scripts.onload = function() {  
            callback();  
            document.body.removeChild(this);  
        };  
        scripts.onreadystatechange = function() {  
            if (this.readyState == "loaded") {  
                callback();  
                document.body.removeChild(this);  
            }  
        };  
        scripts.charset = "GBK";  
        scripts.src = url;  
    }  
    _GetJsData('http://www.uefirst.com/index.js',isok);  
    var isok=function(){alert('isok')};