仅对空白空间进行RegEx验证； 应该接受单词/字符之间的空格

Question

I'm writing reg ex for UI validation for following requirements:

1. It should contain alphabets and/or numbers.
2. It can contain "_"(the only acceptable Special character).
3. "white space" in between the characters can be acceptable.
4. No empty space (only white spaces are not allowed).

Here's my reg ex:

Validators.pattern('^[A-Za-z0-9? ,_-]+$')

Now except '#4', everything else is working fine. It's just accepting only white space; whereas as per requirement white space can be allowed only in between characters.

Answer 1

The regex becomes heavier, but you can do this:

Validators.pattern('^[A-Za-z0-9?,_-](\s?[A-Za-z0-9?,_-]+)*$')

This ensures that:

• The first character is a valid character, and not a space
• The string either ends here, or
  • Contains any sequence of [optional whitespace][at least one valid non-whitespace character]

So that these match:

• "aa"
• "a"
• "aa"

And these don't:

• "" (not sure if you want this one to match)
• "a "
• " a"
• "aaa "

Note: I used your pattern, which allows ? , , and - which are not included in your second requirement.