如何检查新日期(“某个日期”)是否能够正确解析?

我有下面的代码,它应该尝试解析给定的日期。如果失败,则默认为当前日期:

var date = new Date(textbox.value); // Try to parse
if (isNaN(date)) date = new Date(); // Default to current

现在我使用isNaN()测试它是否能够正确解析,例如检查new Date()是否返回“Invalid Date”。

这在IE、FF和Chrome上似乎可以正常工作,但在safari上不起作用。例如,如果它试图解析日期的空字符串,有时会认为是1970年,有时会认为是无效日期。以下是来自safari JS控制台的练习:

a=new Date("")  <-- This thinks it's 1970 for some reason
Thu Jan 01 1970 11:00:00 GMT+1100 (AUS Eastern Daylight Time)

b=new Date("abc") <-- Fails of course, which is good
Invalid Date

c=new Date("") <-- Why does this fail now, whereas it thought it was 1970 before?
Invalid Date

isNaN(a)  <-- Why is it successfully parsing an empty string for a date?
false

isNaN(b)  <-- Fair enough
true

isNaN(c)  <-- This is what i'd expect, but why is it different now?
true

不知道这里发生了什么,非常感谢