I’m looking for some help writing a custom validator (using validator_calc)  which will allow only letters, numbers, and spaces in the field. If anyone can help out, that would be appreciated!
I would just use a regular expression for this, just define it within the pattern key like so…
{
    ...
    "validator": "regexp",
    "pattern": "[\w\d ]*",
    ...
}
            Thank you, that’s what I needed! I didn’t know the proper syntax for how to do it in in a validator, so the pattern key was exactly what I needed to know.