JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/SteveSanderson/knockout.mapping/master/build/output/knockout.mapping-latest.js"></script>
<select data-bind="options: List1Items, 
                   optionsText: 'name',                                                        
                   value: List1SelectedItem,
                   optionsCaption: 'Please Select...'"></select>
<br/>

<select data-bind="visible: List1SelectedItem,
                   options: List2Items, 
                   optionsText: 'name',                                                        
                   value: List2SelectedItem,
                   optionsCaption: 'Please Select...'"></select>
<br/>
<select data-bind="visible: List2SelectedItem,   
                   options: List3Items, 
                   optionsText: 'name',                                                        
                   value: List3SelectedItem,
                   optionsCaption: 'Please Select...'"></select>

JavaScript

var list1Items = '[{"id": "1","name": "list1item1"},{"id": "2","name": "list1item2"}]';
var list2Items = '[{"id": "1","name": "list2item1"},{"id": "2","name": "list2item2"}]';
var list3Items = '[{"id": "1","name": "list3item1"},{"id": "2","name": "list3item2"}]';

ViewModel = function () {  
    var self = this;
    
    self.List1 = ko.mapping.fromJSON(list1Items);
	self.List1SelectedItem = ko.observable();
	self.List1SelectedItem.subscribe(function () {
        self.List2([]);
		self.List2SelectedItem(undefined);
        //ajaxcall to populate list 2
        self.List2(ko.mapping.fromJSON(list2Items)());
	});

	this.List2 = ko.observableArray();
	self.List2SelectedItem = ko.observable();
	self.List2SelectedItem.subscribe(function () {
        self.List3([]);
		self.List3SelectedItem(undefined);
        //ajaxcall to populate list 3
        self.List3(ko.mapping.fromJSON(list3Items)());
	});
    
    this.List3 = ko.observableArray();
	self.List3SelectedItem = ko.observable();    
}

ko.applyBindings(new ViewModel());