JavaScript异步加载方案

JavaScript异步加载方案

function loadscript(url, callback){   var script = document.createElement("script")   script.type = "text/javascript";   if (script.readyState){ //IE      script.onreadystatechange = function(){         if (script.readyState == "loaded" || script.readyState == "complete"){ script.onreadystatechange = null; callback();         }      };   } else { //Others: Firefox, Safari, Chrome, and Opera      script.onload = function(){          callback();      };   }   script.src = url;   document.body.appendChild(script);}