Is there a Regular Expression for blank input?

Question

这可能是一个愚蠢的问题，但是有一个正则表达式来验证blanks或根本没有用户输入吗？

Answer 1

Start of line immediately followed by end of line:

^$

Any amount of whitespace, including none:

^\s*$

Answer 2

^$ should do the trick. ^ matches the beginning and $ the end of the string.