Knockout Validation - Dynamic Validation Message

I'm using the 'equal' validation rule. self.FirstName = ko.observable(); self.Lastname = ko.observable(); self.ValidationMessage = ko.computed(function(){ return 'This is my dy

Solution 1:

you dont need self.ValidationMessage. instead use a function as message and it will get called dynamically.

functionvm() {
  var self = this;
  self.FirstName = ko.observable();
  self.LastName = ko.observable().extend({
    equal: {
      message: function(params, observable) {
        return'First Name: ' + params + ' and Last Name: ' + observable() + ' are not the same.';
      },
      params: self.FirstName
    }
  });
}

ko.applyBindings(newvm());

.validationMessage { display: block; }

<scriptsrc="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script><scriptsrc="https://cdnjs.cloudflare.com/ajax/libs/knockout-validation/2.0.3/knockout.validation.min.js"></script><inputdata-bind="textInput: FirstName"><inputdata-bind="textInput: LastName">