js 跨域请求失败

注：错误返回：Failed to load http://xxxxxxxxxxx: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://m.cd.com' is therefore not allowed access

　　如:

$.post("http://",data,function(result){
	console.log(result);
               alert(result);
	if(result == 'true'){
		alert('预约成功');
	}else if(result == 'false'){
		alert('预约失败');
	}else{
		alert(result)
	}
},'json')

　解决方法:

　　

1.如果请求的是的url是PHP的，须要PHP中文件前头加入 

echo header("Access-Control-Allow-Origin:*");

　　

2.如果请求的html的，这需要加入 

<meta http-equiv="Access-Control-Allow-Origin" content="*">