RegEx to allow letters numbers and spaces but not two spaces in a row

问题

Hello I have a RegEx that allows up to 18 characters with numbers, letters and spaces only.

How can I modify this to check if the string is starting with a space, or has two spaces in a row?

/^[0-9A-Za-z\s]{1,18}$/

I am using this regex in both native javascript (not jquery) and PHP.

回答1:

You can use a negative look-ahead to check if the string starts with a space or has 2 or more consecutive spaces, something like:

^(?!.*\s{2,})(?!^ )[0-9A-Za-z\s]{1,18}$

回答2:

(?:(?![ ]{2}).)+

use this regex. This may solve your problem.

来源：https://stackoverflow.com/questions/36902258/regex-to-allow-letters-numbers-and-spaces-but-not-two-spaces-in-a-row