如何使用JQuery验证正则表达式不需要的字段

Question

I have a form in my web and I'm using the JQuery validation plugin. I have a 'comment' that I want to be NOT required (it can be empty), but has to match a specific regular expression if filled.

Using this, if the field is empty, the validation returns false (not valid), and the error is shown:

'comment':{
     required: false,
     regexp: /^([-a-z0-9_ ()])+$/i,
},

How can I achieve the intended behaviour?

Answer 1

Try:

/^[-a-z0-9_ ()]+$|^$/i

I just added another match for emptiness