function loadScript(url,callback){
var script=document.createElement("script");
script.type="text/javascript";
if(script.readyState){
script.onreadystatechange=function(){
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script.onreadystatechange=null;
callback();
};
}
}else{
script.onload=function(){
callback();
};
};
script.src=url;
document.getElementsByTagName("head")[0].appendChild(script);
};