Knockout Validation with Msg

by Dejan Vasic

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.0/knockout-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout-validation/2.0.3/knockout.validation.min.js"></script>
<div>
  <input type="text" data-bind="value: firstName"/>
  <span data-bind="text: firstName"></span>
</div>

JavaScript

ko.validation.rules['mustEqual'] = {
    validator: function (val, otherVal) {
        return val === otherVal;
    },
    message: 'The field must equal {0}'
};
ko.validation.registerExtenders();


function Person(){
	this.firstName = ko.observable().extend({ mustEqual: 5 });
}

var viewModel = new Person();
viewModel.firstName('Yo');

ko.applyBindings(viewModel);