js动态加载，并调用其中方法

function appendJs(url,callback){
	var script = document.createElement("script");
	script.type = "text/javascript";
	script.charset = "utf-8";
	script.src = url;
	if(script.readyState){
		script.onreadystatechange = function(){
			if(script.readyState=="loaded" || script.readyState=="complete"){
				callback.call(null);
				script.onreadstatechange  = null;
			}
		}

	}else{
		script.onload = function(){
			callback.call(null);
		}

	}
	document.getElementsByTagName("head")[0].appendChild(script);
}
appendJs("http://www.test.com/myapp/test2.js",function(){
	testJs();

});