JSFiddle - React, Tailwind, and code Playground

HTML

<select id="selectmenu1" name="" data-theme="c" data-bind="options: contacts, optionsValue: 'ContactID', optionsText: function(i) { return i.FirstName + ' ' + i.LastName }, optionsCaption: 'Choose...'">        
</select>

JavaScript

var ViewModel= {
    contacts: [{
ContactID: 0,
FirstName: "Aaa",
LastName: "bbb",
MobileNumber: null,
StartDate: "0001-01-01T00:00:00",
EndDate: "0001-01-01T00:00:00"
},
{
ContactID: 0,
FirstName: "Ccc",
LastName: "ddd",
MobileNumber: null,
StartDate: "0001-01-01T00:00:00",
EndDate: "0001-01-01T00:00:00"
}
]
}
ko.applyBindings(ViewModel);