Question

Everything I’ve found indicates that an empty string can be matched in a regular expression by /^$/. However, that expression is not working in my Mongoose Validator for zipcode.

I want to set zipcode if one of two states is true – either it is empty or it is a valid, five digit number.

ZIP_REGEX: /^$|^[0-9]{5}$/
zip: {
    type: Number,
    validate: [ ZIP_REGEX, 'ValidationError']
},

This validator fails each time I attempt to store an empty string. The result is I can set valid zipcode, but never unset them. Is Mongoose also trying to verify that the empty string is a Number? Is the regular expression wrong?

Answer 1

Use a custom validation function for anything a bit unusual like this. Assuming you want to support both numbers and strings as input:

function validator(v) {
    return (!v && v !== 0) || /^[0-9]{5}$/.test(v.toString());
};

zip: {
    type: Number,
    validate: [validator, 'ValidationError']
},