the run results is ok,but I don't know why come out this mistake.thanks. the browser is Chrome. Error:Error in event handler for (unknown): TypeError: Cannot read property 'checked' of null. at Object.SL_BBL_locer
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
<script type="text/javascript">
window.onload=function(){
window.addEventListener('message',function(e){
var color=e.data;
console.log(color);
},false);
window.frames[0].postMessage('getcolor','http://localhost:8080/HelloWorld/onMessage.jsp');
}
</script>
</head>
<body>
<iframe id="child" src="http://localhost:8080/HelloWorld/onMessage.jsp"></iframe>
</body>
</html>