JS实现动态添加外部js、css到head标签的方法

function appendJQCDN() {   var head = document.head || document.getElementsByTagName('head')[0];   var script = document.createElement('script');   var style = document.createElement('style');   script.setAttribute("src", "https://cdn.bootcss.com/jquery/1.10.2/jquery.min.js");   style.innerHTML = '';   head.appendChild(script);   head.appendChild(style);}

function loadScript(url, callback) {   var script = document.createElement("script");   script.type = "text/javascript";   if (typeof (callback) != "undefined") {     if (script.readyState) {       script.onreadystatechange = function () {         if (script.readyState == "loaded" || script.readyState == "complete") {           script.onreadystatechange = null;           callback();         }       };     } else {       script.onload = function () {         callback();       };     }   };   script.src = url;   document.body.appendChild(script);}

loadScript("https://cdn.bootcss.com/jquery/3.2.1/jquery.js", function() {    //加载,并执行回调函数   alert('动态引入jquery成功')});