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')
});