javascript动态加载js文件

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