JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://knockoutjs.com/downloads/knockout-3.1.0.js"></script>
<select multiple="multiple" data-bind="selectedOptions: selected, options: options, valueAllowUnset: true"></select>

CSS

select {
  width: 100px;
}

JavaScript

var vm = {
    selected: ko.observableArray(),
    options: ko.observableArray(['a', 'b', 'c', 'd'])
};
setTimeout(function () {
    vm.selected(['a', 'c']);
}, 1000);
ko.applyBindings(vm);