function load() {
        var script=document.createElement("script");
        script.type="text/javascript";
        script.src="/html/js/contabs.js";//你要加载的js路径
        document.getElementsByTagName('head')[0].appendChild(script);
        script.onload=function(){alert('成功加载')}
    }
    load();

延迟两秒执行

setTimeout("load()",2000);//延时2秒