JSFiddle - React, Tailwind, and code Playground

HTML

<input data-bind="value: loginText, valueUpdate: 'afterkeydown'">
<input type="password" data-bind="value: passwordText, valueUpdate: 'afterkeydown'">
<button data-bind='click: makeWrong'>Make it wrong</button>
<div class="alert alert-danger" data-bind="visible: isError">Something is wrong</div>

JavaScript

function User() {
    var self = this;
    self.loginText      = ko.observable(null);
    self.passwordText   = ko.observable(null);
    self.isError        = ko.observable(false);
    
    self.makeWrong = function(){
        self.isError(true);
    }
    
    ko.computed(function() {
    debugger;
        self.loginText();
        self.passwordText();
        self.isError(false);
    });
}

ko.applyBindings(User);