JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.3.0/knockout-debug.js"></script>
<form id="testform">
    <input id="test" type="text" data-bind="textInput: test" />
    <button type="button" data-bind="click: testClick">Change Value With JS</button>
</form>

JavaScript

function vm() {
    var self = this;
    
    self.test = ko.observable("test");
    
    self.testClick = function () {
        $("#test").val("test2");
    
        alert("Observable isn't updated when JS changes input value.\n\nObs value: " + self.test());
    }
}

ko.applyBindings(new vm(), $("#testform")[0]);