Question

I am having this issue where I want an INPUT field to be just NUMBERS or EMPTY.
If a user chooses to add a phone number or leave it blank if they don’t want to.

I tried using this, but it requires a phone number if it’s empty:

 "onlyNumberSp": {
                "regex": /^[0-9\ ]+$/,
                "alertText": "* Numbers only"
            },

Thank you

Answer 1

/^[0-9]*$/ allows any amount of digits, including none at all (= empty string).

In case you want to keep whitespace allowed, use /^[0-9 ]*$/ (no need to escape the space character).