问题
I am more or less a regex novice. I tried to get the following conditions into a regex:
- No White Space at the beginning and at the end of a string
- Allow all digits
- Allow spaces, points, brackets, plus and minus
Resulted in the following regex:
^\S[\d\/. ()\-+]*\S$
But now i try to apply two more conditions:
- Allow only one or two +
- Allow only one ( and one )
My problem is how to merge those two conditions into the existing regex string above cuz excluding + [+]{1,2} and () [(]{1} [)]{1} doesn't make much sense cuz i try to make general statements in no particular order so that i would be able to chain it. Thanks Ralf
回答1:
Use this:
^(?=\S)(?=(?:[^+]*\+){0,2}[^+]*$)(?=(?:[^(]*\()?[^(]*$)(?=(?:[^)]*\))?[^)]*$)[- .()+0-9]*[-.+()0-9]$
In the regex demo you can play with the input to check what matches and doesn't.
Explanation
- The
^anchor asserts that we are at the beginning of the string - The lookahead
(?=\S)asserts that what follows is a non-space character - Lookahead
(?=(?:[^+]*\+){0,2}[^+]*$): two+chars at the most - Lookahead
(?=(?:[^(]*\()?[^(]*$): One(at the most - Lookahead
(?=(?:[^)]*\))?[^)]*$): One)at the most [- .()+0-9]*zero or more of the allowed chars[-.+()0-9]end with one of the allowed chars that is not a space- The
$anchor asserts that we are at the end of the string
Reference
- Lookahead and Lookbehind Zero-Length Assertions
- Mastering Lookahead and Lookbehind
回答2:
First, get rid of those \S, they are wrong. Each one will match any non-whitespace character, so if for instance I put a $ at the beginning of the phone numer, it will still match.
^[\d\/. ()\-+]+$
Now, let's add some conditions, and for that, we can use lookaheads:
- One or two
+:(?=[^+]*(?:\+[^+]+){0,2}[^+]*$)(non-consecutive and not at the end of a string) - One
(and one):(?=[^()]*(?:\([^()]*\))?[^()]*$)
So the expression becomes:
^(?=[^+]*(?:\+[^+]+){0,2}[^+]*$)(?=[^()]*(?:\([^()]*\))?[^()]*$)[\d\/. ()\-+]+$
Regex101: http://regex101.com/r/xW5pS7/1
This technique lets you basically apply multiple regexes over the same matched string to add constraints. The lookaheads have a $ anchor at the end, so they both have to match the whole string.
But I have a feeling your requiremens are too loose, and this expression will match too much. If you can think of more precise rules, I'll include them in my answer.
来源：https://stackoverflow.com/questions/24922540/multiple-conditions-in-validation-regex