function loadScript(url,callback){
var script = document.createElement("script");
script.type = "text/javascript";
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.getElementsByTagName("head")[0].appendChild(script);
}
loadScript('file1.js',function(){
loadScript('file2.js',function(){
alert("file file2 loaded!")
});
})