Add custom message to knockout required validation

Question

I have added a required validation to my observable. How can I change the message to something other than "This field is required."

self.Leaving = ko.observable(leaving).extend({
    required:   {
        onlyIf: function() { return self.Status() == 10; }
    }              
});

Answer 1

self.Leaving = ko.observable(leaving).extend({
    required:   {
        onlyIf: function() { return self.Status() == 10; },
        message: 'Custom message'
    }
});