HTML5 Regex Pattern Validation

Question

The validation I need is the following A-Z, a-z, 0-9, no trailing/leading whitespace, -._ only once non-trailing/leading

Till now I have the following:

<input type="text" pattern="^\S[a-zA-Z0-9]*\S$">

This takes care of the leading trailing whitespace and A-Z,a-z,0-9, but it needs minimum 2 characters

Then I thought of something like this for the symbols -._

<input type="text" pattern="^\S[a-zA-Z0-9]*[\-_+]{,1}\S$">

But no luck there. Any ideas?

could you provide some examples for valid and invalid matches? — Avinash Raj
– Avinash Raj, Commented Dec 1, 2014 at 11:33

nhahtdh · Accepted Answer · 2014-12-01 11:40:00Z

3

Since pattern attribute uses the same syntax as JavaScript, you can use the following regex:

<input type="text" pattern="^(?=..)[a-zA-Z0-9]*([_.-][a-zA-Z0-9]*)?$">

^{You can test with the snippet above by typing something in, then change focus from the input.}

The input can only contain a-zA-Z0-9 and at most once of _.-. The look-ahead in front (?=..) checks that there are at least 2 characters.

answered Dec 1, 2014 at 11:40

nhahtdh

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