JSFiddle - React, Tailwind, and code Playground
HTML
<select data-bind="foreach: opts, value: val">
<option data-bind="text: name, value: id"></option>
</select>
<span data-bind='text: val'></span>
JavaScript
var vm = {
opts: [{id: 1, name: 'a'}, {id: 2, name: '2'},{id: 3, name: '3'}],
val: ko.observable(1)
};
vm.val.subscribe(function (x) {
console.log(x, typeof x);
});
ko.applyBindings(vm);