Custom Validators

Custom validators are just functions which accept the following parameters:

parameter

type

meaning

value

String

The current value of the field being validated.

field

schema.field object

The schema for the field being validated.

model

model object

The relevant model.

Note: If you don't need all the parameters, your function doesn't have to use them.

Synchronous Validators

This is a simple example of a synchronous US Zip Code validator function, that just takes the current value:

zipcode(value) {
let re = /(^\d{5}$)|(^\d{5}-\d{4}$)/;
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if (!re.test(value)) {
return ["Invalid Zip Code."];
} else {
return []
}
};

Note: There's a built-in regular expression validator that you could also use for validating zip codes.

Asynchronous Validators

Asynchronous validators are also supported. This allows you to perform validations that might take a long time: a complex calculation, or validation via AJAX, for example.

These are very similar to synchronous validators, but they should return a promise, which resolves to an array of errors:

let customAsyncValidator = function(value) {
return new Promise((resolve, reject) => {
setTimeout(() => {
if (value)
resolve();
else
resolve([ "Invalid value from async validator" ]);
}, 1000);
});
};