JSFiddle - React, Tailwind, and code Playground
HTML
<div ng-app="myApp" ng-controller="myCtrl">
<select ng-model="firstSelect" ng-options="option.id as option.name for option in parentOptionObjs"></select>
<select ng-model="secondSelect" ng-options="option.name for option in childOptionObjs | secondDropdown: firstSelect"></select>
</div>