动态加载脚本

	    //普通通浏览器  FireFox  Opera Chrome Safari 3+
	var script=document.createElement("script");
	script.type="text/javascript";
	script.onload=function(){
		alert('Script load');
	};
	script.src="file1.js";
	document.getElementsByTagName("head")[0].appendChild(script);
	   //IE中
	var script=document.createElement("script");
	script.type="text/javascript";
	script.onreadyStatechange=function(){
		if(script.readyState=="load"||script.readyState=="complete"){
			script.onreadyStatechange=null;
			alert('Script load');
		}
	}
	script.src="file1.js";
	document.getElementsByTagName("head")[0].appendChild(script);






	//综合卸载一起
	function loadScript(url,callback){
       var script=document.createElement("script");
	   script.type="text/javascript";
	   if(script.readyState){
	   	script.onreadyStatechange=function(){
	   		if(script.readyState=="load"||script.readyState=="complete"){
			   script.onreadyStatechange=null;
			   callback();
		    }
	   	}
	   }
	   else{
	   	  script.onload=function(){
		     callback();
	      };
	   }
	   script.src="file1.js";
	   document.getElementsByTagName("head")[0].appendChild(script);
	}
	
	//调用loadScript
	loadScript("file1.js",function(){
		alert('Script load');
	});
	//载入多个脚本
	loadScript("file1.js",function(){
		loadScript("file2.js",function(){
			loadScript("file3.js",function(){
				alert('Script load');
			});
		});
	});