RegExp check if it's a number while it's not empty

I'm using开发者_如何学运维 vbulletin and I can set to custom fields regexp.

I've created a custom field that are userids and only accepts numbers, so the regexp I'm using is:

\d+

But I need to allow it to be empty. Any ideas?

Thanks

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\d*

where * indicates 0 or more digits

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Then use this:

\d*

This means zero or more digits. Zero digits naturally means it is empty.

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Assuming your framework wraps it with the appropriate anchors, just transform that to

\d*

which matches any number of digits, including 0 digits.

/^\d*$/

would be better if nothing is anchoring that for you.

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Change this plus (1 or more) to a star (0 or more).