JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <select data-bind="options: addresses, value: address, optionsCaption: 'Select...'"></select>
</div>

JavaScript

function VM() {
    var self = this;

    self.addresses = [
        "123 Main Street, Somewhere, MI",
        "456 South Street, New York, NY"];

    self.address = ko.observable();

    self.address.subscribe(function (sel) {
        // parse sel to find state
        self.state("WI");
    });
}

ko.applyBindings(new VM());