原生JS实现动态加载js文件并在加载成功后执行回调函数的方法

function loadScript(src, callback) {
 var script = document.createElement('script'),
  head = document.getElementsByTagName('head')[0];
 script.type = 'text/javascript';
 script.charset = 'UTF-8';
 script.src = src;
 if (script.addEventListener) {
  script.addEventListener('load', function () {
   callback();
  }, false);
 } else if (script.attachEvent) {
  script.attachEvent('onreadystatechange', function () {
   var target = window.event.srcElement;
   if (target.readyState == 'loaded') {
    callback();
   }
  });
 }
 head.appendChild(script);
}

loadScript('http://cdn.staticfile.org/jquery/1.6.2/jquery.min.js',function(){
 console.log('onload');
});

function sk_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);
}

if(typeof jQuery=='undefined'){
	sk_loadScript("/comments/js/jquery.js",function(){
		sk_main();
	});
}else{
	sk_main();
}