Regular Expression to validate empty fields

Question

I have a form that use a regular expression that validate decimals and natural numbers, but I have a problem, this doesn't validate empty fields. My expression regular is this :

"^([0-9])+\.[0-9]|[0-9]$"

what can I do in order to this regular expression validate empty fields? thanks.

score 3 · Answer 1 · answered Mar 22 '14 at 17:34

Use this regular expression to handle both number(only positive) and empty.

^(?:[0-9]+(?:\.[0-9]+)?)?$

Explanation of the regex is:

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (optional
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    [0-9]+                   any character of: '0' to '9' (1 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    (?:                      group, but do not capture (optional
                             (matching the most amount possible)):
--------------------------------------------------------------------------------
      \.                       '.'
--------------------------------------------------------------------------------
      [0-9]+                   any character of: '0' to '9' (1 or
                               more times (matching the most amount
                               possible))
--------------------------------------------------------------------------------
    )?                       end of grouping
--------------------------------------------------------------------------------
  )?                       end of grouping
--------------------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string

Thanks guys, I proved all of your suggestions but It not resolved my problem at all, still allow to enter empty fields, I maybe not explain very well, I would like that my regular expression does not permit to register empty fields. — Jeason, Mar 26 '14 at 20:31
@Jeason you are right, you didn't explain it well. We got you mean to allow empty and that caused the problem. So, the fix is just remove the `?` before the `$`. Finally it will be `^(?:[0-9]+(?:\.[0-9]+)?)$` and it will not allow any empty. — Sabuj Hassan, Mar 27 '14 at 07:46

aliteralmind · Answer 2 · 2014-03-22T17:39:59.550

1

Do you mean this?

"^(?:([0-9])+\.[0-9]*|[0-9]|)$"

This regex contains an additional possibility of no characters.

edited Mar 22 '14 at 17:39

answered Mar 22 '14 at 17:34

aliteralmind

19,847
17
77
108

score 0 · Answer 3 · answered Mar 22 '14 at 17:35

Try:

^([0-9]+\.[0-9]*|[0-9]*)$

This:

fixes the problem that only exactly 1 digit was accepted after the decimal dot,
fixes the problem you had that you only accepted natural numbers of a single digit,
fixes the problem that the beginning and end of the field were not matched in both cases,
allows 0 digits, which is an empty field.

score 0 · Answer 4 · answered Mar 26 '14 at 20:31

0

Thanks guys,

I proved all of your suggestions but It not resolved my problem at all, still allow to enter empty fields, I maybe not explain very well, I would like that my regular expression does not permit to register empty fields.

answered Mar 26 '14 at 20:31

Jeason

1
2

Regular Expression to validate empty fields

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