Validation
validationType is a Yup type (string number boolean date array object); validations is a list of { name, params } where name is a Yup method. The message is the last parameter, and a friendly default is used when omitted:
{ "name": "required", "params": ["Please tell us your name"] }
{ "name": "min", "params": [3, "At least 3 characters"] }
{ "name": "matches", "params": ["^[0-9]{5}$", "Five digits please"] }
On a boolean field, required means "must be ticked". A rule whose value is empty is ignored.
Available rules by validationType:
| Type | Rules |
|---|---|
string | required min / max / length (characters) email url uuid matches (regex string) lowercase uppercase oneOf / notOneOf (list of values) sameAs / notSameAs (another field) |
number | required min max moreThan lessThan integer positive negative oneOf / notOneOf sameAs / notSameAs minField / maxField (another field) |
date | required min max (earliest / latest date) minField / maxField (not before / not after another field) |
array | required min max length (number of choices) |
boolean | required (must be ticked) |
file (used automatically for type: "file") | required maxFileSize (MB per file) fileTypes ([".pdf", "image/*"]) minFiles maxFiles |
Phone and e-mail checks: phone (a number that exists in its country's numbering plan, checked with libphonenumber-js: length and leading digits), phoneCountries ([["dk", "se"], "message"]: only numbers from these countries) and emailDomains ([["company.com"], "message"]: only addresses on these domains, subdomains included).
Not every rule makes sense for every input: the builder offers them per kind of input, through rulesFor(field) / RULES_BY_KIND (a phone number gets phone, phoneCountries, matches, sameAs…; a URL url, maxLength, matches; a dropdown, a Likert or a ranking only required).
Rules that compare with another field take that field's model as their value, e.g. { "name": "sameAs", "params": ["email", "The emails do not match"] } or { "name": "minField", "params": ["startDate", "End must be after the start"] }. If the referenced field no longer exists the rule is ignored. A file field's attributes.accept is enforced on submit too, not just used as a hint for the file picker.