动态加载js

function load_js(src) {

            var xml_http = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();

            xml_http.onreadystatechange = function() {

                if (xml_http.readyState == 4) {

                    var script_element = document.createElement('script');

                    document.getElementsByTagName('head')[0].appendChild(script_element);

                    script_element.text = xml_http.responseText;

                }

            }

            xml_http.open('GET', src, true);

            xml_http.send('');

}

调用方法：

 if (! +[1, ]) {

load_js("js/excanvas.js");//如果是ie浏览器就加载js
}

http://www.perfgeeks.com/?p=543