try<script language="javascript">
var x;
if (typeof x == 'undefined')
{
try
{
if (!x)
alert("x exists, but was not assigned yet");
}
catch(e)
{
alert("x doesn't exist");
}
} if (typeof y == 'undefined')
{
try
{
if (!y)
alert("y exists, but was not assigned yet");
}
catch(e)
{
alert("y doesn't exist");
}
}
</script>
var x;
if (typeof x == 'undefined')
{
try
{
if (!x)
alert("x exists, but was not assigned yet");
}
catch(e)
{
alert("x doesn't exist");
}
} if (typeof y == 'undefined')
{
try
{
if (!y)
alert("y exists, but was not assigned yet");
}
catch(e)
{
alert("y doesn't exist");
}
}
</script>
解决方案 »
免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货