JavaScript 之 动态加载JS代码或JS文件

<script type="text/javascript">
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("jquery-latest.js", function () { //加载,并执行回调函数
  alert($(window).height());
});
//loadScript("jquery-latest.js"); //加载js文件
</script>