動態加載jquery

function withjQuery(callback) {
  if(!(window.jQuery)) {
    var js = document.createElement('script');
    js.setAttribute('src', 'https://dynamic.12306.cn/otsweb/js/common/jquery-1.4.2.min.js?version=5.47');
    js.setAttribute('type', 'text/javascript');
    js.onload = js.onreadystatechange = function() {
        if (!this.readyState || this.readyState === 'loaded' || this.readyState === 'complete') {
                if(callback && typeof callback === "function") {
                   callback();
                }
            js.onload = js.onreadystatechange = null;
        }
    };
    document.getElementsByTagName('head')[0].appendChild(js);
  }
}
 
withjQuery( 
   function() { 
      $(function(){ 
           alert("jQuery loaded");
            //將連接爲/zixun的url修改成商務通地址
            var local = location.href;
		    var refer = document.referrer;
			var swturl ="http://swt.jingkangyiyuan.cn/LR/Chatpre.aspx?id=PGD31671888&lng=cn&r="+refer+"&p="+local;
			$("a[href='/zixun']").attr("href", swturl);
      })(); 
   }
);